CHAPTER 3 (2)

4541/ CHEMISTRY MODUL PEMBELAJARAN

CHAPTER 3 ; CHEMICAL FORMULAE AND EQUATION

CHAPTER 3: CHEMICAL FORMULAE AND EQUATIONS

1

CHEMICAL FORMULAE

AND EQUATION

Concepts of relative atomic mass and

relative molecular mass

Relationship between the number of moles with the

number of particlesRelationship between the

number of moles of a substance with its mass

Relationship between the number

of moles of a gas with its volume

Chemical formulae

Chemical equations

1.What is the meaning of

relative atomic mass ?

2.What is the meaning of

relative molecular mass?

3.What is the relative molecular mass for : i) Oxygen ii) Ammonia.

1.What is mole ?

2.What is Avogadro number ?3.How many molecules are there in 2.0 mol ammonia, NH3 ?4. How many atom are there in 2.0 mol ammonia, NH3 ?

1.What is Molar mass.

2.Calculate the molar mass for (NH4)2CO3 ?3.What is the mass for 1.5 mol MgO ?4.What is the number of mole in 22 g carbon dioxide?

1.What is Molar

volume ?

2.What is the volume of (i) 2 mol O2 (ii) 16 g O2

(iii)3.01 x 1023 O2

1.What is empirical formula ?2.What is molecular Formula ?

1.Write the chemical equation to represent decomposition process of calcium carbonate ?2. Write the chemical equation to represent the reaction between magnesium and oxygen ?3. Write the chemical reaction when sulphuric acid is react with potassium hydroxide ?


CONCEPT MAPCHAPTER 3: CHEMICAL FORMULAE AND EQUATIONS


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Chemical equationChemical equation

CHEMICAL FORMULAE

Number of moles of a substance

Number of moles of a substance

Empirical formulaEmpirical formula Molecular formulaMolecular formula

ReactantsProducts

ReactantsProducts

Avogadro Constant, NAAvogadro

Constant, NA

Number of particles

Number of particles

Volume of gas

Volume of gas

Molar volumeMolar

volume

Mass of a substance

Mass of a substance

Molar massMolar mass

Relative atomic mass

(RAM)

Relative atomic mass

(RAM)

Relative molecular

mass (RMM)

Relative molecular

mass (RMM)

Relative formula mass

(RFM)


(RFM)

The simplest formula

The simplest formula

The actual formula

The actual formula

CH2OCH2OC6H12O6C6H12O6

contains

needed to form

needed to determine

divided into

related to

1 mol is

1 mol is

1 mol is

is classified into

is is

example example

1 Magnesium atom 2 atom of Carbon-12

Ar Mg = 24 OR The Mg atom is twice as heavy as the carbon-12 atom 1/12 x 12 2 x 12 = 24 = 24


A. RELATIVE ATOMIC MASS AND RELATIVE MOLECULAR MASS

1. Carbon-12 is chosen as a standard to compare the masses of atoms because it is a …………… and can be easily …………………


3

R.A.M = The average mass of one atom of an element The mass of an atom of hydrogen

OR

R.A.M = The average mass of one atom of an element 1/12 x the mass of an atom of Carbon-12

R.M.M =

OR

R.M.M =

RELATIVE ATOMIC MASS AND

RELATIVE MOLECULAR MASS

MeaningRelative Atomic Mass, Ar

(R.A.M)

oo

The masses of atom and molecules are very small. For example hydrogen is the smallest atom and the mass of hydrogen atom, H is 0.000 000 000 000 000 000 000 001 4 g and the mass of methane molecule, CH4 is 0.000 000 000 000 000 000 000 022 4 g.

This masses are very small and inconvenient to use. Imagine if you want to write all those zeroes every time you want to do a chemical calculation.

In practice, chemists do not use these actual masses of atoms and molecules in their calculation. They use relative masses. This means they simply compare the masses of atoms and molecules.

The lightest atoms are the hydrogen atom. When the masses of atoms were first compare, they were all compare with the mass of one hydrogen atom. A nitrogen atom is 14 times as heavy as a hydrogen atom. So nitrogen was said to have Relative Atomic Mass of 14.

Chemists later found that comparing masses of atoms with the mass of a hydrogen atom was not very convenient. In 1961, it was decided to compare masses of atoms with the mass of carbon atom.

A carbon atom has 12 times the mass of one hydrogen atom. So 1/12 of carbon atom has the same mass as one hydrogen atom.

Relative Molecular Mass, Mr

(R.M.M)


2. The relative atomic mass of an elements is the .....................................................

……………………………………………………………………………………………..

Relative atomic mass of an element =

3. Since relative atomic mass compares the masses of atoms, it does not have any

…………………

(i) How many times is copper atom heavier than two helium atom?

[Relative atomic mass (RAM) : He = 4; Cu = 64 ]

Solution: Mass of a copper atom = RAM of copperMass of 2 helium atom 2 x RAM of helium

= 64 2 x 4 = 8 times

(ii) How many times is one atom of silicon heavier than one atom of lithium?

[Relative atomic mass: Li = 7; Si = 28 ]

(iii) The mass of one Z atom is 4 times larger than the mass of one nitrogen atom.Calculate the relative atomic mass of Z.

[Relative atomic mass: N = 14 ]

4. The relative molecular of a molecule is the .........................................................

……………………………………………………………………………………………

Relative molecular mass of an element =


4

Calculate the Relative Molecular Mass

&Relative Formula Mass


Example of relative molecular masses of some molecular substances:[ Relative atomic mass (RAM) : H = 1 ; C = 12 ; N = 14 ; O = 16]

Molecular substance Relative molecular massWater, H2O 2 x RAM of H + 1 x RAM of O


5

Examples:[R.A.M; H=1, C=12, N=14, O=16]

1. R.M.M CO2 = 12 + 2(16) = 44

2. R.M.M NH3 =

3. R.M.M CH3COOH =

4. R.M.M C6H12O6 =

Examples:[J.A.M; C=12, O=16, Na=23, Mg=24; Al=27, S=32, Cu=64]

1. R.F.M MgO = 24 + 16 = 40

2. R.F.M CuSO4 =

3. R.F.M Al2(CO3)3 =

4. R.F.M Na2S2O3 =

Molecular Compound Ionic Compound

Relative molecular mass/Relative formula mass can be calculated by adding up the relative atomic mass of all the

atoms that are present in the molecule/formulae.


= 2(1) + 1(16)= 2+ 16 = 18

Sulphur dioxide, SO2 1 x RAM of S + 2 x RAM of O

Methane, CH4

5. Example of relative formula masses of some ionic substances:Molecular substance

Chemical formula


Sodium chloride NaCl 1 x RAM of Na + 1 x RAM of Cl = 1(23) + 1(35.5)= 23 + 35.5= 58.5

Magnesium sulphate

MgSO4

Ammonium carbonate

(NH4)2CO3

Aluminium nitrate Al(NO3)3

Calcium hydroxide Ca(OH)2

Hydrated copper(II) sulphate

CuSO4.5H2O

B. THE MOLE AND THE NUMBER OF PARTICLES

1. A mole is …………………………………………………………………………………..


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2. The Avogadro constant, NA is defined as…………………………………………..………………………………………………………………………………………

3. One mole of substance contains …………………………….. particles.

4. Complete the relationship between the number of moles and the number of particles:

C. THE MOLE AND THE MASS OF SUBSTANCES

1. The mass of one mole of any substance is called ………………………………..

2. Unit for molar mass is ……………………………..

3. Complete the following table:Element Relative mass Mass of 1 mol Molar mass

Helium, He 4 4g 4 g mol-1

Sodium, Na 23Water , H2OAmmonia , NH3

Sodium chloride, NaCl [ Relative atomic mass (RAM) : H,1 ; O, 16 ; N, 14 ; Na, 23 ; Cl, 35.5 ]

5. Complete the relationship between the number of moles and the mass of a substance:

6. [Relative atomic mass: H = 1; N = 14; O =16; Cl = 35.5; Ca = 40; Zn = 65 ]

i. Calculate the number of mole of :

(a) 2.0 g calcium, Ca (b) 3.2 g oxygen gas, O2

Number of mole of Ca= Number of mole of O2== 0.05 mol = ……… mol


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Number of moles

x NA

………….

2.040

Number of moles

x Molar mass

………….


(ii) What is the mass of :

(a) 0.1 mol ammonia, NH3 ? (b) 0.25 mol zinc chloride, ZnCl2 ?

Mass of NH3 = ……... Mass of ZnCl2 =

= ……. g = ……… g

7. Calculate the number of moles found in 9.5g of magnesium chloride, MgCl2. (Relative atomic mass: Mg, 24; Cl, 35.5)

8. Calculate the mass in gram found in 0.3 mol of magnesium chloride, MgCl2.

(Relative atomic mass: Mg, 24; Cl, 35.5)

9. How many chloride ions are there in 19g of magnesium chloride, MgCl2. (Relative atomic mass: Mg, 24; Cl, 35.5. Avogradro constant: 6.02 x 1023)

10. Calculate the mass in gram of 3 x 1022 units of magnesium chloride, MgCl2. (Relative atomic mass: Mg, 24; Cl, 35.5. Avogradro constant: 6.02 x 1023)

D. THE MOLE AND THE VOLUME OF GAS

1. The …………………… of a gas is defined as the volume occupied by one mole of the gas.

2. Complete the relationship between the number of moles and the volume of a gas:


8


3. Construct a mind map to show the relationship between the number of particles, the number of moles, mass of substances and volume of gases.

4. Diagram below shows three balloons filled with different gas at room conditions.


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Number of moles

Molar volume

Volume of gas ( dm3)

Mass (g)Number of particles

Number of moles

X ………..

…………..

X …………...

………….. …………..

X ………...

Number of moles

Number of moles

32.0 g

Oxygen, O2

gas 6.02 × 1023

molecules

Carbon dioxide, CO2

gas24.0 dm3

Hydrogen, H2 gas


(a) Complete the table below :

Type of gas Hydrogen, H2 Oxygen, O2Carbon dioxide,

CO2

Volume of gas / dm3 24.0

Mass / g 32.0

Number of molecules / molecules

6.02 × 1023

Number of moles / mol

E. CHEMICAL FORMULAE

1. A chemical formula is a ………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………………………………

2. An empirical formula is a formula that shows …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

3. A molecular formula is a formula that shows …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

whereby n is a positive integer

Based on the statement above, complete the table below:

Compound Empirical formula Molecular n


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Molecular formula = ( )n


formulaWater H2O 1Ethene C2H4

Carbon dioxide CO2

Glucose CH2O 6Benzene C6H6

4. 2.24 g of iron combines chemically with 0.96g of oxygen to form an oxide. What is the empirical formula of the oxide ? [ Relative atomic mass: O, 16; Fe, 56 ]

Element Iron, Fe Oxygen, OMass (g) 2.24 0.96Number of moles of atoms

Ratio of moles

Simplest ratio of moles

The empirical formula of the oxide is ………………….

5. Copper (II) iodide contains 20.13% of copper by mass. Find its empirical formula. [ Relative atomic mass : Cu,64 ; I, 127 ]

Based on its percentage composition, 100g of copper(II) iodine contains 20.13g of copper. So, taking 100g of the compound.

element Cu IMass (g) 20.13 100 - 20.13 =

79.87Number of moles of atomsRatio of molesSimplest ratio of moles

The empirical formula of the oxide is ………………

6. Tobacco contains nicotine. Chemical analysis of the compound shows that nicotine contains :


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Determine the empirical formula of nicotine.[ Relative atomic mass : H = 1; C = 12; N = 14 ]

Element C H N

Percents (%) 74.10 8.64

Mass in 100 g of nicotine / g

Number of moles (mol)

Ratio of moles

Simplest ratio of moles

The empirical formula of the compound is ………………

7. A gaseous hydrocarbon R contains 80 % of carbon and 20 % of hydrogen.6 g of this hydrocarbon occupies a volume of 4.48 dm3 at STP.Determine :

(a) the empirical formula of R(b) the relative molecular mass of R(c) the molecular formula of R

[ Relative atomic mass : H = 1; C = 12 ; 1 mol of any gas occupies 22.4 dm3 at STP ]

CHEMICAL FORMULAE ; Determine Empirical Formula of Substances

Describe an experiment to determine empirical formula of magnesium oxide


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74.10 % carbon8.64 % hydrogenand the rest is nitrogen

Element Mg O

Mass (g) y-x z-y

Number of moles

Simplest ratio of moles a b


Lid

Magnesium ribbon Crucible

Heat

Procedure:1. Clean magnesium ribbon with sand paper2. Weigh crucible and its lid3. Put magnesium ribbon into the crucible and weigh the crucible with its lid 4. Heat strongly the crucible without its lid5. Cover the crucible when the magnesium starts to burn and lift/raise the lid a little at

intervals6. Remove the lid when the magnesium burnt completely7. Heat strongly the crucible for a few minutes8. Cool and weigh the crucible with its lid and the content9. Repeat the processes of heating, cooling and weighing until a constant mass is

obtained10. Record all the mass

Result:Observations Inferences

Magnesium burns brightly Magnesium is a reactive metalWhite fumes are released and form a white solid substance

Magnesium oxide is produced

The mass increases Magnesium has combined with oxygen

Data:Mass/g

Crucible + lid xCrucible + lid + magnesium yCrucible + lid + magnesium oxide z

Calculations:

Empirical formula: MgaOb / MgO

Chemical Formulae – Empirical formula of Copper(II) oxide


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The empirical formula for copper(II) oxide can be determine base on the reaction between copper(II) oxide and hydrogen gas. The apparatus is shown below.

(a) Label the diagram below.

(b) List the material and the apparatus that used in this experiment

Material : …………………………………………………………………………………………

Apparatus : ………………………………………………………………………………………

………………………………………………………………………………………

(c) Describe how you can prepare dry hydrogen gas that is use to react with copper(II) oxide.

………………………………………………………………………………………………………

………………………………………………………………………………………………………

………………………………………………………………………………………......................

(d) The reaction between copper(II) oxide and hydrogen can be represent by the word equation below . Fill in the blank with correct word.


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Copper (II) oxide + Hydrogen ………………… + ………….

(d) What is the colour of :

(i) Copper(II) oxide : ……………………………………………………………

(ii) Copper : ……………………………………………………………

(e) A student performs an experiment to determine the empirical formula of copper(II) oxide. The steps and setup of the apparatus for the experiment is shown in the diagram bellow.

Steps Apparatus arrangement

1. Combustion tube and porcelain crucible are weighed.

2. Combustion tube, porcelain crucible and copper(II) oxide are weighed.

copper(II) oxide

3. Combustion tube, porcelain crucible and copper are weighed.

copper

(i) State in the table below, two observation and inferences which can be made from the experiment .


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25.10 g

27.10 g

26.70 g


Observation Inference

(ii) Determine the empirical formula cf copper(II) oxide.

Complete the formula of some common cations and anions in the table below:


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Cation Formula Anion Formula

Sodium ion Chloride ion

Potassium ion Bromide ion

Zinc ion Iodide ion

Magnesium ion Oxide ion

Calcium ion Hydroxide ion

Iron(II)ion Sulphate ion

Iron(III) ion Carbonate ion

Copper(II) ion Nitrate ion

Ammonium ion Phosphate ion

Tin (II) ion Sulphide ion

Lead(II) ion Sulphite ion

*Tips : Method to memorise the cations and anions.


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+1 Na+ H+ K+ Ag+ Li+

Nak Hafal Kimia Agak Liat

+3 Fe3+ Al3+

Fetrah Alam

+2 Cu2+ Ba2+ Ca2+ Pb2+

CuBa CakaPb Mgapa ZnFe

Mg2+ Zn2+


CHEMICAL FORMULAE AND EQUATIONS – Chemical formulae of ionic compounds

1. Ionic compounds consist of cations(positive ions) and anions(negative ions)2. To construct chemical formulae of ionic compounds, we need to know the formulae of cations and anions.

Activity : Complete the table below of some common cations.

3. Ionic compounds contain charge particles. Their chemical formulae are electrically neutral because the total positive charges are equal to the total negative charges.


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-1 OH-

OH NO Baru Clear Fikiran I

-2 SO42+ S2- CO3

2- O2-

SOS Contact Osama

NO3-

Br-

Cl-

F-

Name of cation Formula Charge of cation

Litium ion Li+ +1

Sodium ion +1

Potassium ion K+

Hydrogen ion +1

Silver ion Ag+

Ammonium ion

Calcium ion Ca2+ +2

Zinc ion

Magnesium ion Mg2+

Iron(II) ion +2

Copper(II) ion

Lead(II) ion Pb2+

Barium ion +2

Iron(III) ion Fe3+

Aluminium ion +3

Chromium(III) ion +3

Name of anion Formula Charge of anion

Fluoride ion F- -1

Chloride ion -1

Iodide ion -1

Hydroxide ion OH- -1

Nitrate ion -1

Nitrite ion NO2- -1

Oxide ion O2- -2

Carbonate ion -2

Sulphide ion S2- -2

Sulphite ion SO32-

Sulphate ion SO42- -2

Thiosulphate ion S2O32-

Chromate(VI) ion CrO42-

Dichromate(VI) ion Cr2O72-

Phosphate ion PO43-


4. After you have already know the formula of cations and anions , follow the steps given below how to construct the chemical formula of compounds.

4.1 Write the name of compounds4.2 Identify and write the name of cation and anion 4.3 Write the formula of its cation and anion4.4 Determine the number of catoins and anions by balancing the positive and negative charge4.5 Write the number of cations and anions as subscript number

Example 1 : Construct the chemical formula of sodium chloride

Solution : Name of compound sodium chloride Name of ions sodium ion and chloride ion Formula of ions Na+ Cl-

Balancing the charge 1(+1) 1(-1) No. of cations and anions as subscribe Na1Cl1 Chemical formula NaCl

Example 2 : Construct the chemical formula of Magnesium chloride

Solution : Name of compound magnesium chloride Name of ions magnesium ion and chloride ion Formula of ions Mg2+ Cl-

Balancing the charge 1(+2) 2(-1) No. of cations and anions as subscribe Mg1Cl2 Chemical formula MgCl2

Example 3 : Construct the chemical formula of Zinc sulphate

Solution : Name of compound zinc sulphate Name of ions zinc ion and sulphate ion Formula of ions Zn2+ SO4

2-

Balancing the charge 1(+2) 1(-2) No. of cations and anions as subscribe Zn1(SO4) 1

Chemical formula ZnSO4

Example 4 : Construct the chemical formula of Sodium oxide

Solution : Name of compound sodium oxide Name of ions sodium ion and oxide ion Formula of ions Na+ O2-

Balancing the charge 2(+1) 1(-2) No. of cations and anions as subscribe Na2O1

Chemical formula Na2O

Example 5 : Construct the chemical formula of Sodium carbonate

Solution : Name of compound sodium carbonate Name of ions sodium ion and carbonate ion Formula of ions Na+ CO3

2-

Balancing the charge 2(+1) 1(-2) No. of cations and anions as subscribe Na2(CO3)1

Chemical formula Na2CO3

Example 6 : Construct the chemical formula of Aluminium sulphate


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Solution : Name of compound aluminium sulphate Name of ions aluminium ion and sulphate ion Formula of ions Al3+ SO4

2-

Balancing the charge 2(+3) 3(-2) No. of cations and anions as subscribe Al2(SO4)3

Chemical formula Al2(SO4)3

Example 7 : Construct the chemical formula of Copper chloride

Solution : Name of compound copper(II) chloride Name of ions copper(II) ion and chloride ion Formula of ions Cu2+ Cl-

Balancing the charge 1(+2) 2(-1) No. of cations and anions as subscribe Cu1(Cl)2

Chemical formula CuCl2

5. Try to construct chemical formula of each compound

1. Construct the chemical formula of aluminium chloride

Solution : Name of compound ………………………………………….

Name of ions ………………………………………….

Formula of ions …………………………………………

Balancing the charge …………………………………………

No. of cations and anions as subscribe …………………………………………

Chemical formula …………………………………………

2. Construct the chemical formula of aluminium oxide


Name of ions ………………………………………….





3. Construct the chemical formula of calcium carbonate


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Name of ions ………………………………………….





8. Write the chemical formulae and names for the common ionic compound :

O2-(oxide)

CO32-

(carbonate)SO4

2-(sulphate)

Cl-

(chloride)Br-

(bromide)I-

(iodide)OH-

(hydroxide)NO3

-

(nitrate)

K+

(potassium)Na+

(sodium)H+

(hydrogen)Ag+

(silver)NH4

+

(ammonium)Ca2+

(calcium)Cu2+ (copper)

Mg2+

(magnesium)Zn2+

(zinc)Pb2+

(lead)Al3+

(aluminium)


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9. Write chemical formulae for the following substances:

Substance FormulaType of particle



Sodium Sulphate

Zinc carbonate

Ethanoic acid

Ammonium carbonate

Ammonium nitrate

Ammonia gas

Magnesium nitrate

Silver chloride

Magnesium

Hydrochloric acid

Sulphuric acid

Zinc

Potassium oxide

Nitric acidCopper(II) sulphate

Magnesium oxide

Hydrogen gas

Iodine

Lead(II) carbonate

Carbon dioxide

Chlorine

Iron(II) sulphate

Oxygen gas

Sodium hydroxide

Magnesium chloride

Aluminium sulphate

Ammonia aqueous

Zinc sulphate

Lead(II) chloride

Ammonium chloride

Silver nitratePotassium

iodideNitrogen

dioxide gas

CHEMICAL EQUATIONS


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2 mol hydrochloric acid reacts with 1 mol copper(II) carbonate to form 1 mol copper(II) chloride , 1 mol water and 1 mol carbon dioxide


CHEMICAL EQUATIONChemical equation is a shorthand description of a chemical reaction. A → B + CReactant ProductsA + B → CReactants ProductA + B → C + D


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CHEMICAL EQUATIONS

Interpret Chemical Equation

Writing chemical equation

Numerical problems involving chemical

equations.

1. Identify the reactants and the product. Metal + Oxygen → Metal oxide Metal + Chlorine → Metal chloride Metal + Acid → Salt + Hydrogen Metal carbonate → Metal oxide + Carbon dioxide Metal carbonate + Acid → Salt + Water + Carbon dioxide Acid + Metal oxide → Salt + Water Acid + Alkali → Salt + Water AX + BY → AY + BX

2. Write the chemical formulae for the reactant and the product3. Balanced the chemical .(The number of atoms on each side of the equation must be equal/same)

Steps to solve numerical problems:1. Write a chemical equation.2. Identify information from the

equation.(e.g: mass, volume)3. Determine the number of

mole from the information given.

4. Relate/compare the mole ratio of the related substances

5. Convert the number of moles to mass/volume

Example:When 20 g of calcium carbonate, CaCO3 is heated strongly, calcium oxide and carbon dioxide is form. Calculate(a) the mass of calcium oxide form. (b) the volume of carbon dioxide produced.

Reactants → Products

2HCl + CuCO3 → CuCl2 + H2O + CO2

Example: Reaction between copper(II) oxide and hydrochloric acid.

1. Copper(II) oxide + Hydrochloric acid → Copper(II) chloride + Water

2 CuO + HCl → CuCl2 + H2O

3 CuO + 2HCl → CuCl2 + H2O

∆

∆


Reactants Products

Low of conservation of matter : Matter can be neither created nor destroyedFor writing symbol equations :

1. You must know the product of the reaction.

1.1 Metal + oxygen → metal oxide1.2 Non metal + oxygen → non metal oxide1.3 Metal + chlorine → metal chloride1.4 Metal carbonate → metal oxide + carbon dioxide1.5 Metal + acid → metal salt + hydrogen1.6 Acid + alkali → salt + water1.7 Acid + base → salt + water1.8 Acid + metal carbonate → salt + carbon dioxide + water1.9 Ammonia gas + hydrogen chloride gas → ammonium chloride1.10 AX(aq) + BY(aq) → AY(s) + BX(aq)

example : Lead(II) nitrate + Potassium iodide → Lead(II) iodide + Potassium nitrate (colourless solution) (colourless solution) (yellow precipitate) (colourless solution)1.11 Metal nitrate → metal oxide + nitrogen dioxide + oxygen

2. You must know how to write the reactant and the product in formula form.3. All the elements that appear on the left hand side are also found on the right hand side.4. The number of atoms of each element at both side must be same.(Balance the equation)5. You cannot change the formula of the chemical to get the equation to balance.6. The state of reactants and products are represent by the letter (s) for solid, (l) for liquid, (g)

for gas and (aq) for aqueous (dissolved in water)7. Base on the equations, we can also describe quantitative composition of substances that

involved in chemical reactions. The coefficients in a balanced equation tell us the exact proportion of reactants and products in chemical reaction. For example base on the equation below :

2H2 (g) + O2 (g) → 2 H2O (l) We can said that :

(i) Hydrogen gas react with oxygen gas to produce water (ii) Hydrogen and oxygen are the reactants, water is the product.(iii) 2 moles of hydrogen gas react with one mole of oxygen gas to form 2 moles of

water.

Activities for writing chemical equation :

A. Burning of magnesium ribbon in air(oxygen)


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1. Clean 3 cm of magnesium ribbon with sand paper. 2. By using the tong, burn the magnesium ribbon3. Write your observation

Observation

Name of reactants

Name of product

Chemical equation

B. Heating of Copper(II) carbonate

Copper(II) carbonate

1. Put one spatula of copper(II) carbonate powder into the test tube.Note its colour.2. Set up the apparatus as shown above.3. Heat the copper(II) carbonate and pass the gas produced through lime water. Record the observation.

Observation

Name of reactant

Name of products

Chemical equation

C. Precipitation of lead(II) iodide

Lead(II) Potassium iodide, KI


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Lime water Heat


nitrate, Pb(NO3)2

1. Pour 2 cm3 of lead(II) nitrate solution into a test tube.2. Pour 2 cm3 of potassium iodide solution into another test tube.3. Pour the potassium iodide solution into the lead(II) nitrate solution and shake the mixture.4. Record your observation.

Observation

Name of reactants

Name of products

Chemical equation

D. Formation of ammonium chloride

………………………………………………………………………………………………………

………………………………………………………………………………………………………

………………………………………………………………………………………………………

white fume, ammonium chloride

Hydrogen chloride gas Ammonia gas

Concentrated hydrochloride acid Concentrated ammonia solution

Observation

Name of reactants

Name of product

Chemical equation

F) CHEMICAL EQUATIONS

1. ………………………………… is a shorthand description of a chemical reaction.2. The starting substances are called ……………………………….3. ……………………………………...are called products.4. Information obtained from chemical equation:

(i) Qualitative aspect : type of …………………….. and ………………


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involved in the chemical reaction and the ……… of each reactant and product.

(ii) Quantitative aspect : ………………… of reactants and products involved in the chemical reaction that is coefficients involved in a balanced equation of the formulae of reactants and products.

5. Write a balanced chemical equation for each of the following reactions:a. Zinc carbonate Zinc oxide + carbon dioxide

……………………………………………………………………………………

b. Sulphuric acid + sodium hydroxide sodium sulphate + water

……………………………………………………………………………………

c. silver nitrate + sodium chloride silver chloride + sodium nitrate

……………………………………………………………………………………

d. copper(II) oxide + hydrochloric acid copper(II) chloride + water

……………………………………………………………………………………

e. magnesium + oxygen magnesium oxide

……………………………………………………………………………………

f. sodium + water sodium hydroxide + hydrogen

……………………………………………………………………………………

g. potassium oxide + water potassium hydroxide

……………………………………………………………………………………

h. zinc oxide + nitric acid zinc nitrate + water

……………………………………………………………………………………

i. lead(II) nitrate lead(II) oxide + nitrogen dioxide + oxygen……………………………………………………………………………………

6.

How many moles of potassium are needed to reacts with 0.5 mole of bromine gas ?


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2K (s) + Br2 (g) 2KBr (s)


7. 35 g of aluminium reacts with excessive copper (II) oxide powder to produce aluminium oxide powder and copper. Find the number of copper atoms produced.[Relative atomic mass : Al, 27 ; Avogadro constant : 6.02 x 1023 mol-1]

8.

What is the mass of zinc needed to produce 2.4 dm3 of hydrogen gas at room conditions ?[Relative atomic mass : Zn, 65 ; Molar volume 24 dm3 mol-1 at room conditions]


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Zn (s) + 2HNO3 (aq) Zn(NO3)2 (aq) + H2 (g)


PAPER 1: OBJECTIVE QUESTIONS

1.

Based on the statement above, what is the relative atomic mass of element Z?[Relative atomic mass : Te, 128 ]

A 8B 16 C 32D 64

2.

What is the molecular formula of compound X?[Relative atomic mass: C,12; H,1]

A CH2

B C2H4

C C2H6

D C3H6

3. Zn + 2HCl → ZnCl2 + H2

Based on the equation above, calculate the volume of hydrogen gas released at room conditions when 1.3 g of zinc powder reacts with excess hydrochloric acid.


29

8 atoms of element Z have the same mass as in 1 atom of tellurium, Te.

3.0 g of carbon reacts with 0.5 g of hydrogen gas to form compound X.

Relative molecular mass of compound X is 42.


[ Molar volume : 24 dm3mol-1 at room conditions, Relative atomic mass: H,1; Cl,35.5; Zn, 65]

A 120 cm3

B 240 cm3

C 360 cm3

D 480 cm3

4. A hydrocarbon has the empirical formula of CH3 with a molar mass of 30 g mol-1. Which of the following is the molecular formula of the hydrocarbon?[Relative atomic mass : H, 1; C,12 ]

A CH3

B C2H6 C C3H9

D C4H12

5. The equation below shows the chemical equation of the combustion of ethanol in excess oxygenPersamaan di bawah menunjukkan persamaan kimia bagi pembakaran etanol dalam oksigen berlebihan

2C2H5OH + 7O2 4CO2 + 6H2O

What is the volume of carbon dioxide gas released when 9.20 g ethanol reacts completely?Berapakah isi padu gas karbon dioksida terbebas apabila 9.2 g etanol bertindak balas lengkap?

[Relative atomic mass of H = 1, C = 12, O = 16, 1 mol of gas occupies 24 dm3 at room condition][Jisim atom relatif H = 1, C = 12, O = 16, 1 mol of gas memenuhi 24 dm3 pada keadaan bilik]

ABCD

4.8 cm3

9.6 cm3

96.0 cm3

9600 cm3

6. What is the number of atoms in 1 mol of nitrogen dioxide gas , NO2? [ Avogadro constant = 6.02 X 1023 mol-1]

Berapakah bilangan atom yang terdapat dalam 1 mol gas nitrogen dioksida, NO2? [Pemalar Avogadro = 6.02 X 1023 mol-1]

A 1.505 X 1023 atoms1.505 X 1023 atom

B 6.02 X 1023 atoms


30


6.02 X 1023 atom

C 1.806 X 1024 atoms1.806 X 1024 atom

D 3.01 X 1024 atoms3.01 X 1024 atom

7. The diagram below shows the volume of oxygen gas.Rajah di bawah menunjukkan isipadu gas oksigen.

Which of the following gases occupies the same volume as the gas?[ Relative atomic mass: H=1, He=4, N=14 and 1 mole of gas occupies a volume of 24dm3 at room temperature]

Antara gas-gas yang berikut, yang manakah mempunyai isipadu yang sama dengan gas tersebut?[ Jisim atom relatif: H=1, He=4, N=14 dan 1 mol gas menempati isipadu 24dm3 pada suhu bilik]

I 2 g of helium gas,He 2 g gas helium,He

II 2 g of hydrogen gas,H2

2 g gas hidrogen,H2

III 7 g of nitrogen gas,N2

7 g gas nitrogen,N2

IV 8.5 g of ammonia gas,NH3 8.5 g gas ammonia,NH3

A I and III onlyI dan III sahaja

B II and III onlyII dan III sahaja

C II and IV onlyII dan IV sahaja

D I and IV onlyI dan IV sahaja

8. The equation below shows the reaction between zinc and nitric acid.Persamaan di bawah menunjukkan tindakbalas antara zink dan asid nitrik.


31

12000cm3 of oxygen gas 12000cm3 gas oksigen


Zn(s) + 2HNO3 (aq) Zn(NO3)2 (aq) + H2(g)

Which of the following statements is correct?[Relative atomic mass of H =1, Zn= 65, N= 14, O= 16 ]

Persamaan di bawah menunjukkan tindakbalas antara zink dan asid nitrik.

Zn(p) + 2HNO3 (ak) Zn(NO3)2 (ak) + H2(g)

Antara pernyataan yang berikut, yang manakah betul?[Jisim atom relatif : H =1, Zn= 65, N= 14, O= 16 ]

A 1 g of zinc react with 2g of nitric acid to produce 1g of zinc nitrate and 1g of hydrogen gas1g zink bertindak balas dengan 2 g asid nitrik menghasilkan 1 g zink nitrat dan 1 g gas hidrogen

B 65g of zinc react with 126g of nitric acid to produce 189g of zinc nitrate and 2g of hydrogen gas65g zink bertindak balas dengan 126 g asid nitrik menghasilkan 189g zink nitrat dan 2 g gas hidrogen

C 1 zinc atom reacts with 2 nitric acid molecule to produce 1 zinc nitrate molecule and 1 hydrogen gas molecule1 atom zink bertindak balas dengan 2 molekul asid nitrik menghasilkan 1 molekul zink nitrat dan 1 molekul gas hidrogen

D 1 mol of zinc react with 2 mol of nitric acid to produce 1 mol of zinc nitrate and 2 mol of hydrogen gas1 mol zink bertindak balas dengan 2 mol asid nitrik menghasilkan 1 mol zink nitrat dan 2 mol gas hidrogen

9 Which of the following fertilizers contains the highest percentage of nitrogen?[Relative atomic mass: H= 1, N=14, O=16, Al=27, K=39]

Antara baja-baja yang berikut, yang manakah mengandungi peratus nitrogen yang paling tinggi?[Jisim atom relatif: H= 1, N=14, O=16, Al=27, K=39] A NH4NO3

B (NH4)2SO4

C KNO3

D CO(NH2)2

10 When 8.3 g of a metal oxide of Z is heated with carbon, 5.9 g of the metal Z is obtained. What is the empirical formula of the metal oxide ?


32


[Relative atomic mass: O=16, Z=59]

Apabila 8.3 g oksida logam Z dipanaskan dengan karbon, 5.9 g logam Z terhasil.Apakah formula empirik bagi oksida logam tersebut? [Jisim atom relatif : O=16, Z=59]

A ZO2

B Z2O

C Z2O3

D Z3O2

11 The following equation shows the decomposition reaction of magnesium carbonate salt, when heated at room temperature and pressure.

Persamaan berikut menunjukkan tindak balas penguraian garam magnesium karbonat, apabila dipanaskan pada suhu dan tekanan bilik

MgCO3 MgO + CO2

What is the mass of magnesium carbonate are needed to produce 2.0g of magnesium oxide?

Berapakah jisim magnesium karbonat yang diperlukan untuk menghasilkan 2.0g magnesium oksida?. [Relative atomic mass: C= 12, O= 16, Mg= 24] [ Jisim atom relative : C= 12, O= 16, Mg= 24 ]

A 0.05g

B 0.48g

C 2.00g

D 4.20g

12. The chemical equation shows the burning process of ethene in excess air.

What is the maximum volume of carbon dioxide gas evolved when 0.5 mole of ethene burns completely?[1 mole of gas occupied 24 dm3 at room temperature and pressure]

A 12 dm3

B 24 dm3

C 36 dm3

D 48 dm3


33

C2H4(g) + 3O2 2CO2(g) + 2H2O(l)


13. Decomposition by heat of lead(II) nitrate can be represented by the following chemical equation,

2Pb(NO3)2(p) 2PbO(p) + 4NO2(g) + O2(g)

What is the mass of oxygen gas given off when 33.1 g of lead(II) nitrate decompose completely?Relative atomic mass O = 16, N = 14 and Pb = 207

A 1.6 gB 3.2 gC 16.0 gD 32.0 g

14. The chemical formula for glucose is C6H12O6. This shows that

I the empirical formula for glucose is CH2OII each glucose molecule is made up of 6 carbon atoms, 12 hydrogen atoms and 6

oxygen atoms.III 1 mol of glucose contains a total of 144 x 1023 atomsIV One glucose molecule has a mass of 180 times higher than the mass of 1

hydrogen atomUse the information relative atomic mass for H =1,C =12 and O =16 Avogadro Constant = 6.02 X 1023 mol-1

A I and II onlyB I, III and IV onlyC II, III and IV onlyD I, II, III and IV

15. What is the percentage by mass of nitrogen content in urea, CO(NH2) 2 ?Use the information that the relative atomic mass of C = 12 , N =14, H=1

and O = 16

A 23.3 % B 31.8 %C 46.7 %D 63.6 %


34


16.

Which of the following conclusions can be drawn from the above statement?

I 1 mol of W has 8 times more atoms than 1 mol of Q

II 1 atom of W is 8 times heavier than 1 atom of Q

III 1 atom of W has the same number of protons with 8 atoms of Q

IV 56 g of W has the same number of atoms as in 7 g of Q

A I and III only

B II and IV only

C I, II and III only

D I, II, III and IV

PAPER 2 : SECTION A

1. Diagram 1 shows the set up of the apparatus used in an experiment to determine the empirical formula of an oxide of copper


35

Oxide of copper

Burning of excess hydrogen

The relative atomic mass of metal Q is 7 and the relative atomic mass of the metal W is 56


DIAGRAM 1

The following data was obtained:

Mass of combustion tube + porcelain dish = 25.30 g

Mass of combustion tube + porcelain dish + oxide of copper = 53.30 g

Mass of combustion tube + porcelain dish + copper = 47.70 g

(a) What is meant by empirical formula?

.......................................................................................................................................

....................................................................................................................................... [1mark]

(a) Write the chemical equation for the reaction used to produce hydrogen gas.

....................................................................................................................................[1mark]

(c ) Based on the data given,

(i) Calculate the mass of copper and the mass of oxygen contained in the sample of oxide of copper.

Mass of copper ....................................................g.

Mass of oxygen .....................................................g[2 marks]

(ii ) Calculate the mol ratio of copper to oxygen. Given that the relative atomic mass of O = 16, Cu= 64

[2 marks]


36

Dry hydrogen gas

Heat


(iii) Write the empirical formula of the oxide of copper.

...........................................................................................................................[1 mark]

(iv) Write the chemical equation for the reaction between hydrogen and the oxide of copper.

...........................................................................................................................[1 mark]

(c) The empirical formula for magnesium oxide can be determined by direct heating of magnesium. Draw the set up of the apparatus to carry out this experiment.

[2 marks]

2. The following equation is not balanced :

Na2SO4 + BaCl2 BaSO4 + NaCl

(a) Identify the reactants and products of the reaction.

Reactants : ………………………………………………………………………

Products : ………………………………………………………………………[ 2 marks]


37


(b) Write the balanced equation.

……………………………………………………………………………………[ 1 mark]

(c) Calculate :

(i) the number of mole of sodium sulphate that react completely with a solution containing 4.16 g of barium chloride[ Relative atomic mass : Cl = 35.5; Ba = 137 ]

[ 2 marks]

(ii) the mass of barium sulphate formed when 1 mol of sodium sulphate is reacted completely with barium chloride.[ Relative atomic mass : O = 16; S = 32; Ba = 137 ]

[ 2 marks]

(d) In an experiment, when chlorine gas is passed over heated iron wool, a chloride compound with 34.5 % iron by mass is formed. Determine the empirical formula of the chloride compound.[ Relative atomic mass : Cl = 35.5; Fe = 56 ]

[ 3 marks]

3. Diagram 3.1 shows the structural formula of aspirin.


38


Diagram 3.1

(a) (i) What is the molecular formula of aspirin?

……………………………………………………………………………....................[ 1 mark]

(ii) What is the molar mass of aspirin?[ Relative atomic mass: H, 1; C,12; O,16]

[ 1 mark]

(b) Diagram 3.2 shows the structural formula of vitamin C.

Diagram 3.2


39

CC

CC

C

C

O

C

O

C

O

O H

C

H

H

H

H

H

H

H

CC

OC

C

C

H

O

H O

O

H

O H

C

H

O H

H


(i) Write down the molecular formula and empirical formula of vitamin C.[ Relative atomic mass: H, 1; C,12; O,16]

Molecular formula : …………………………………………………………………..

Empirical formula : …………………………………………………………………..[ 2 marks]

(ii) What is the difference between the molecular formula and empirical formula of vitamin C?

………………………………………………………………………………………….

………………………………………………………………………………………….[ 2 marks]

(iii) Calculate the mass of 0.2 mole of vitamin C.

[ 1 mark]

(iv) Determine the percentage of oxygen by mass in a molecular of vitamin C.

[ 1 mark]

(c) The empirical formula of a compound Y is CH2O. If its relative molecular mass is 180, determine the molecular formula of Y.

[ Relative atomic mass: H, 1; C,12; O,16]

[ 2 marks]


40


4 (a) (i) An experiment is conducted to determine the empirical formula of phosphorus oxide. After heating, x gram of phosphorus combines with 0.8g of oxygen to form an oxide with the empirical formula of P2O5. Complete Table 4 and determine the value of x.

(Relative atomic mass O=16, P=31)

Satu eksperimen dijalankan untuk menentukan formula empiric fosforus oksida.Selepas pemanasan, x gram fosforus berpadu dengan 0.8g oksigen untuk membentuk oksida dengan formula empirik P2O5.Lengkapkan Jadual 4 dan tentukan nilai x.

(Jisim atom relatif O=16, P=31)

Element Unsur

P O

Mass Jisim (g)

x 0.8

Number of mole Bilangan mol

x32 ……….

Mole RatioNisbah mol

………. 0.05

Simplest RatioNisbah teringkas

2 ………….

Empirical formulaFormula empirik

P2O5

Value of x Nilai x =

[4 marks] (ii) The relative molecular mass of phosphorus oxide is 284, determine the molecular formula of phosphorus oxide.

Jisim molekul relatif fosforus oksida ialah 284, tentukan formula molekul fosforus

oksida

Use this formula, Molecular formula = (Empirical Formula)n, where n is an integer

Guna rumus ini, Formula molekul = (Formula empiric)n, dimana n adalah nombor bulat


41


[2 marks]

(b) Diagram 4 shows the structural formula of vitamin B6 molecules which is used in medication.

Rajah 4 menunjukkan formula struktur molekul vitamin B6 yang digunakan dalam bidang perubatan.

(Relative atomic mass: H=1, C=12, N=14, O=16) (Jisim atom relatif :H=1, C=12, N=14, O=16)

Diagram 4Rajah 4

(i) Write the molecular formula of vitamin B6

Tuliskan formula molekul vitamin B6

……………………………………………………………………………………………………………………………………………

[1 mark]

(ii) Determine the relative molecular mass of vitamin B6

Tentukan jisim molekul relatif vitamin B6

…………………………………………………………………………………………...[1 mark]

(iii) A capsule contains 0.155 gram of vitamin B6. Calculate the number of moles of vitamin B6 molecules present in the capsule.Sebiji kapsul mengandungi 0.155 gram vitamin B6. Hitungkan bilangan mol molekul vitamin B6 yang hadir di dalam sebiji kapsul.

…………………………………………………………………………………………...

…………………………………………………………………………………………... [1 mark]


42


(iv) Calculate the number of molecules of vitamin B6 molecules that present in b (iii) Hitungkan bilangan molekul vitamin B6 yang ada di dalam b (iii)

(NA = 6 x 1023 mole-1)

………………………………………………………………………………………… …………………………………………………………………………………………

[1 mark]

PAPER 2 : SECTION B

1. (a) Table 1 shows the empirical formula and molecular formula of glucose.

Jadual 1 menunjukkan formula empirik dan formula molekul bagi glukosa.

Empirical Formula /Formula empirik CH2O

Molecular Formula /Formula molekul

C6H12O6

Table / Jadual 1

By using information in Table 1, compare and contrast empirical formula and molecular formula for glucose molecule in terms of type of elements, number of atom for each element and relative mass.


43


Dengan menggunakan Jadual 1, banding dan bezakan formula empirik dan formula molekul glukosa di atas dari segi jenis unsur, bilangan atom setiap unsur dan jisim relatif.[Relative atomic mass / Jisim Atom Relatif: C, 12 ; H, 1; O, 16]

[ 3 marks ]

(b) A student carried out an experiment to determine the empirical formula of an oxide of metal Q. Q is placed below hydrogen in the reactivity series. The set – up of the apparatus is shown in Diagram 1.1.

Seorang pelajar telah menjalankan satu eksperimen untuk menentukan formula empirik satu oksida logam Q. Q berada di bawah hidrogen dalam Siri Kereaktifan. Susunan radas ditunjukkan dalam Rajah 1.1.

Diagram / Rajah 1.1

Result / Keputusan :

Mass of combustion tube + porcelain dish = 38.50 gJisim tiub pembakaran + piring porselin

Mass of combustion tube + porcelain dish + oxide of metal Q = 50.45gJisim tiub pembakaran + piring porselin + oksida logam Q

Mass of combustion tube + porcelain dish + metal Q = 48.85gJisim tiub pembakaran + piring porselin + logam Q

(i) Based on the information above, determine the empirical formula for oxide of metal Q. Berdasarkan maklumat di atas tentukan formula empirik bagi oksida logam Q.

. [Relative atomic mass / jisim atom relatif : Q, 207; O, 16]

[ 3 marks ]


44

Oxide of metal Q / Oksida logam Q

Porcelain dish/ Piring porselin

Heat / Panaskan

Flow of dry hydrogen / Aliran hidrogen kering


(ii) Write the chemical equation for the reaction in the experiment.

Tuliskan persamaan kimia bagi tindak balas dalam eksperimen.

[2 marks ]

(iii) State two precaution steps that need to be taken when carry out this experiment.

Nyatakan dua langkah berjaga-jaga yang perlu diambil semasa menjalankan eksperimen ini.

[2 marks ]

(iv) How can you be sure that the reactions are completed in the above experiment?

Bagaimanakah anda boleh pastikan bahawa tindak balas telah lengkap dalam eksperimen di atas?

[1 mark ]

(c) Metal M is placed above aluminium in the reactivity series. You are required to carry out an experiment to determine the empirical formula of oxide of metal M. Draw a labelled diagram for the set – up of the apparatus of this experiment.

Logam M terletak di atas aluminium dalam siri kereaktifan.Anda dikehendaki menjalankan satu eksperimen untuk menentukan formula empirik oksida logam M. Lukiskan rajah berlabel susunan radas untuk eksperimen ini.

[2 marks]

(d) 2H2(g) + O2(g) 2H2O(l)

(i) State three important information that can be interpreted from the above chemical equation.

Nyatakan tiga maklumat penting yang dapat ditafsirkan daripada persamaan kimia di atas.

[3 marks]

(ii) Based on the chemical equation above, calculate the volume of hydrogen gas at room condition required to produce 10 g of water.

Berdasarkan persamaan kimia di atas, hitungkan isipadu gas hidrogen pada keadaan bilik yang diperlukan untuk menghasilkan 10 g air.[Relative atomic mass / jisim atom relatif : H, 1; O, 16 ; Molar volume of gas at room condition / isipadu molar gas pada keadaan bilik.= 24 dm3]

[4 marks]


45


2. (a) Table 2 shows the incomplete observation for two experiments to construct balanced chemical equation.

Jadual 2 menunjukkan pemerhatian yang tidak lengkap bagi dua eksperimenuntuk membina persamaan kimia yang seimbang.

ExperimentEksperimen

ProcedureProsedur

ObservationPemerhatian

A Copper(II)carbonate is heated and the gas produced is passed through lime water.

Kuprum(II)karbonat dipanaskan dan gas yang terhasil dialirkan melalui air kapur.

Green solid turns black. The lime water turns milky.

Pepejal hijau menjadi hitam.Air kapur menjadi keruh.

B Potassium iodide solution is added to lead(II) nitrate solution.

Larutan kalium iodida ditambah kepada larutan plumbum(II)nitrat.

TABLE / JADUAL 2(i) Based on the observation, name the products in experiment A and write the chemical

equation for the reaction.

Berdasarkan pemerhatian , namakan hasil tindak balas dalam eksperimen A dan tuliskan persamaan kimia bagi tindak balas itu.

[ 3 marks ]

(ii) State one observation in experiment B and name the product.Write the chemical equation for the reaction.

Nyatakan satu pemerhatian dalam eksperimen B dan namakan hasil tindak balas itu. Tuliskan persamaan kimia bagi tindak balas itu.

[ 4 marks ]

(b) The reaction between acid , HX and ionic compound , QY2 can be represented by chemical equation below.

Tindak balas antara asid , HX dan sebatian ion , QY2 boleh diwakili oleh persamaan kimia di bawah.

2HX(aq) +QY2(aq)→ QX2(s) + 2HY(aq).

State three statement to describe the chemical equation above. Suggest an acid of HX and an ionic compound of QY2.

Nyatakan tiga pernyataan untuk menghuraikan persamaan kimia di atas.


46


Cadangkan asid HX dan sebatian ion QY2.[ 5 marks]

(c) The information below is regarding substance X

Maklumat di bawah berkaitan dengan bahan X

(i) Determine the empirical formula of substance X.[Given that the relative atomic mass of C = 12 , H = 1]

Tentukan formula empirik bagi sebatian X[Diberi jisim atom relatif C = 12 , H = 1]

(ii) Determine the molecular formula of substance X.

Tentukan formula molekul bagi bahan X.

(iii) Based on the answers in (a)(i) and (a)(ii) , compare and contrast the empirical formula and the molecular formula.

Berdasarkan jawapan dalam (a)(i) dan (a)(ii), banding dan bezakan formula empirik dan formula molekul.

[ 8 marks]

PAPER 2 : SECTION C

1 (a) Diagram 1 shows the set up of the apparatus to determine the empirical formula of oxide of metal M. M is less reactive than hydrogen.Diagram 1 menunjukkan susunan radas untuk menentukan formula empirik oksida logam M. M kurang reaktif daripada hidrogen


47

Carbon 85.70%Karbon

Hydrogen 14.30%Hidrogen

Relative molecular mass = 56Jisim molekul relatif

Thistle funnelCorong tisel

Oxide of metal MOksida logam M


Diagram 1Rajah 1

(i) State two precautions that must be taken in Part A while carrying out the experiment. Nyatakan dua langkah berjaga-jaga yang perlu diambil di Bahagian A semasa menjalankan eksperimen tersebut?

[2 marks]

(ii) Suggest a suitable chemical substance for X in Part B and state the function of X.Cadangkan satu bahan kimia yang sesuai bagi X di Bahagian B dan nyatakan fungsi X.

[2 marks]

(iii) Describe the reaction that occurs in Part C.Huraikan tindak balas yang berlaku di Bahagian C.

[2 marks]

(iv) Information below shows the results of the experiment.Maklumat di bawah menunjukkan keputusn bagi eksperimen tersebut.


48

Mass of combustion tube + porcelain dish = 52.34 gJisim tabung pembakaran + piring porselin

Mass of combustion tube + porcelain dish + oxide of M = 105.86 gJisim tabung pembaran + piring porslin + oksida M

Mass of combustion tube + porcelain dish + M = 102.02 gJisim tabung pembakaran + piring porselin + M

Dilute hydrochloric acidAsid hidroklorik

cairX

HeatPanaskan

Dry hydrogenHidrogen kering

Part ABahagian A

Part BBahagian B

Part CBahagian C

ZincZink


Determine the empirical formula of the oxide of M:Tentukan formula empirik oksida M

[Relative atomic mass of O =16 , M = 207 ][Jisim atom relatif O =16 , M = 207 ]

[4 marks]

(b) The information below is about hydrocarbon JMaklumat di bawah adalah berkaitan dengan hidrokarbon J

Empirical formula of J is CH2

Formula empirik J ialah CH2

Mass of 1 mole of J = 28 g Jisim 1 mol J = 28 g

Produce by dehydration of alcoholDihasilkan melalui pendehidratan alkohol

(i) Determine the molecular formula for hydrocarbon J.[Relative atomic mass of C =12 , H = 1 ] Tentukan formula molekul bagi hidrokarbon J[Jisim atom relatif C =12 , H = 1 ]

[2 marks]

(ii) Describe an experiment to prepare hydrocarbon J in the laboratory from its corresponding alcohol. In your answer, include the diagram of the appratus set-up, materials used, and procedure.Huraikan satu eksperimen untuk menyediakan hidrokarbon J di makmal daripada alkohol yang sepadan. Dalam jawapan anda, hendaklah termasuk gambar rajah susunan radas, bahan dan prosedur.

[8 marks]

END OF CHAPTER 3


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