Chemistry - LT Scotland

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Chemistry National 4 & 5

Unit 1: Chemical Changes and Structure

Key areas: Chemical Formulae

Background

• Imagine you have been invited to invest in

a company that have just discovered a

new way of making petrol.

• Could this be an easy way to make your

fortune?

• But how much do they need to sell it at to

make a profit and will this be cheaper and

therefore more attractive than normal

petrol?

• In order to work out the minimum price,

you need to know what its going to cost to

make it.

• To find this you will need to know what

your starting chemicals are and how they

react to form your product.

• Chemical formulae, balanced chemical

equations and mole calculations are some

important tools that chemists use to work

out how chemicals react and how much of

each substance they form.

Lesson 1: Naming Chemical Compounds

We are learning

• How to name chemical compounds

I can

• Name different chemical compounds

• If a compound contains just two elements

the compound name consists of the

names of both elements but the last part of

the second name becomes –ide.

• e.g. magnesium and oxygen make

magnesium oxide.

• carbon and chlorine make carbon

chloride.

• If a compound contains more than two

elements and one of them is oxygen the

compound name consists of the names of

both the other elements but the last part of

the second name becomes –ate or –ite

depending on the number of oxygen

atoms.

• e.g. copper, sulfur and oxygen make

copper sulfate.

• sodium, phosphorus and oxygen make

sodium phosphate

ACTIVITY 4.1 Naming Compounds Game

Activity: Copy and Complete

Lesson 1: Naming Chemical Compounds

We are learning

• How to name chemical compounds

I can

• Name different chemical compounds

Lesson 2: Covalent Chemical Formulae

• We are learning: – To write chemical formulae for compounds

using prefixes.

• I can

– Give the correct chemical formulae for

different compounds

Writing Chemical Formula

The CHEMICAL FORMULA tells us the number of ATOMS of EACH ELEMENT which are in a compound.

This molecule has 8 x carbon atoms

10 x hydrogen atoms 4 x nitrogen atoms 2 x oxygen atoms

Prefixes

If the name of the compound contains a PREFIX then we simply write what the name tells us!

Prefix Meaning

Mono one

Di two

Tri three

Tetra four

Penta five

Hexa six

Prefixes

Example 1: Carbon Dioxide 1 carbon joined to 2 oxygen Example 2: Phosphorous Pentachloride 1 phosphorous joined to 5 chlorine Example 3: Dinitrogen Monoxide 2 nitrogen joined to 1 oxygen

Prefixes

Use the PREFIX RULE to work out the chemical formulas for:

(a) Silicon dioxide

(b) Carbon tetrachloride

(c) Sulphur trioxide

(d) nitrogen monoxide

(e) difluorine monoxide

(f) aluminium trichloride

(g) lead dioxide

(h) dinitrogen tetroxide

Lesson 2: Covalent Chemical Formulae

• We are learning: – To write chemical formulae for compounds

using prefixes.

• I can

– Give the correct chemical formulae for

different compounds

Starter

1. Write the formula for the following compounds:

a)Carbon dioxide

b)Carbon monoxide

c)Phosphorus pentachloride

d)Dinitrogen tetraoxide

e)Sulphur trioxide

Lesson 3: Valency Rule

• We are learning – How to use the Valency Rule

• I can – Write chemical formulae for compounds

using the valency rule.

Valency Rule

Group

Number 1 2 3 4 5 6 7 0

Valency 1 2 3 4 3 2 1 0

VALENCY tells us HOW MANY ATOMS an element will combine with

The valency of most elements can be determined from their GROUP

This mean that all elements in GROUP 1 have a VALENCY of 1 all elements in GROUP 6 have a VALENCY of 2

Element Symbol Group Valency

Magnesium

Chlorine

Phosphorus

Sodium

Aluminium

Oxygen

Carbon

Valency Rule

Example 1: Write the formula for phosphorous fluoride.

Step 1 Write chemical symbols for each element Step 2 Identify their valencies Step 3 Cross over the valencies Step 4 Cancel any common factor (Simplify) Step 5 Write the Formulae Omit ‘1’ if present

Valencies can be used to work out the formulae for compounds using the following:

Valency Rule

Example 1: Write the formula for magnesium oxide.

Step 1 Write chemical symbols for each element Step 2 Identify their valencies Step 3 Cross over the valencies Step 4 Cancel any common factor Step 5 Omit ‘1’ if present

Valencies can be used to work out the formulae for compounds using the following:

Write the formula for the following covalent compounds

a) sodium chloride

1.

2.

3.

4.

5.

b) Lithium oxide

1.

2.

3.

4.

5.

Valency rules Write the formula for the following covalent compounds

c) calcium sulphide

1.

2.

3.

4.

5.

d) hydrogen oxide

1.

2.

3.

4.

5.

Valency rules Write the formula for the following covalent compounds

e) boron fluoride

1.

2.

3.

4.

5.

f) potassium nitride

1.

2.

3.

4.

5.

Valency rules Write the formula for the following covalent compounds

g) aluminium oxide

1.

2.

3.

4.

5.

h) Sodium phosphide

1.

2.

3.

4.

5.

Valency rules Write the formula for the following covalent compounds

i) Calcium bromide

1.

2.

3.

4.

5.

ACTIVITY 4.2 Covalent Bonding Pairs Game

Exercise 1: Write the Chemical Formulae for

a) lithium chloride

b) magnesium oxide

c) aluminium fluoride

d) sodium sulphide

e) calcium chloride

f) aluminium oxide

Lesson 3: Valency Rule

• We are learning – How to use the Valency Rule

• I can – Write chemical formulae for compounds

using the valency rule.

Lesson 4: Ionic Chemical Formulae

• We are learning – How to use the charge on an ion to give an

ionic formulae

• I can – Write formulae for ionic compounds.

Starter: Write the Chemical Formulae for

a) sodium chloride

b) calcium fluoride

c) potassium sulphide

d) calcium oxide

e) aluminium sulphide

f) magnesium fluoride

g) lithium bromide

h) aluminium chloride

i) magnesium nitride

Formation of ions

• Atoms of elements in the same group have the same number of outer electrons

• The charge on a metal ion is the same as its group

number. • This is the same as the number of electrons that

would need to be lost to form the stable electron arrangement of a noble gas.

• The charge on a non-metal ion is found by

subtracting the group number from 8. • This is the same as the number of electrons that

would need to be gained to form the stable electron arrangement of a noble gas.

Group 1 2 3 4 5 6 7 0

Valency

Charge

on ion

Writing formulae for simple ionic compounds

Here is how the formula for magnesium chloride is worked out:

Step 1: S symbols Mg Cl

Step 2: V valency 2 1

Step 3: S cross over valency 1 2

Step 4: D divide by common factor

Step 5: F formula is MgCl2

Step 6: I Ionic Formula Mg2+ (Cl-)2

Writing simple ionic formulae

1. Lithium bromide 2. Potassium oxide

Writing simple ionic formulae

3. Calcium fluoride 4. Magnesium sulphide

Writing simple ionic formulae

5. Aluminium chloride

6. Sodium nitride

Writing simple ionic formulae

7. Aluminium sulphide 8. Lithium oxide

ACTIVITY 4.3 Ionic Bonding Pairs Game

Exercise 2: Write the Ionic Formulae

a) sodium chloride

b) calcium fluoride

c) potassium sulphide

d) calcium oxide

e) aluminium sulphide

f) magnesium fluoride

g) lithium bromide

h) aluminium chloride

i) magnesium nitride

Lesson 4: Ionic Chemical Formulae

• We are learning – How to use the charge on an ion to give an

ionic formulae

• I can – Write formulae for ionic compounds.

Starter Write ionic formulae for the following:

a) Calcium oxide

b) Lithium oxide

c) Sodium chloride

d) Boron fluoride

e) Potassium nitride

f) Aluminium oxide

g) Calcium bromide

h) Sodium phosphide

Lesson 5: Transition Metal Formulae

• To write ionic formulae for compounds containing transition metals ions.

Transition Metal Elements with a variable charge- Roman Numerals The TRANSITION METALS do not have a fixed Valency. Their VALENCY is indicated by the ROMAN NUMERAL in their name.

Number Roman Numeral

1 (I)

2

3

4

5

6

Transition Metal Elements with a variable charge- Roman Numerals We still use the VALENCY RULE to get their formula. Example 1: Copper (I) oxide Example 2: Iron (II) chloride

Ionic formulae for transition metal compounds

• iron(III) chloride • copper(II) sulphide

• Copper (I) chloride • Iron (II) bromide

Ionic formulae for transition metal compounds

• Lead (I) oxide • Vanadium (V) oxide

Ionic formulae for transition metal compounds

Exercise 3

a) iron(III) chloride

b) copper(II) oxide

c) copper(I) chloride

d) iron(II) bromide

e) lead(I) oxide

f) vanadium(V) oxide

g) copper(II) bromide

h) lead(IV) oxide

Starter Write ionic formulae for the following: 1.Copper (II) oxide 2. Iron (III) chloride 3. Iron (II) bromide 4. Titanium (IV) oxide 5. Vanadium (V) oxide 6. Lead (IV) oxide

Lesson 6 Compounds with group ions

• We are learning – How to write formulas for compounds

containing group ions

• I can – Write ionic formulae for compounds

containing group ions.

Group Ions

Sometimes ions can consist of more than one ATOM – these are called GROUP IONS. The charge is on the WHOLE GROUP and not on one specific atom. e.g. the sulphate ion:

SO42-

The valency of the ion is 2

Formula for the ion

Group ions are normally indicated by the ending –ite or -ate

The valency of the group ion is given by the number of the charge.

This table can be found on pg 8 of your data booklet.

The formula for the Group ions are found on pg 8 of the DATA BOOK

The most common Group Ions are:

Group Ion Formula Charge

carbonate CO32- 2-

nitrate

sulphate

phosphate

hydroxide

sulphite

ammonium

Examples of Group Ions

1. nickel(II) sulphate 2. Copper(II) sulphite

3. magnesium hydroxide 4. ammonium chloride

Examples of Group Ions

5. Sodium phosphate 6. Ammonium carbonate

Examples of Group Ions

Exercise 4

a) sodium sulphate b) potassium nitrate

c) calcium carbonate d) magnesium hydroxide

e) ammonium chloride f) lithium sulphate

g) aluminium carbonate h) lithium carbonate

i) ammonium hydroxide j) aluminium hydroxide

k) ammonium sulphate l) sodium phosphate

m) potassium hydroxide n) radium sulphate

o) sodium sulphite p) ammonium carbonate

Exercise 5

a) potassium chloride b) copper(I) sulphide

c) sodium nitrate d) magnesium oxide

e) iron(II) sulphate f) ammonium hydroxide

g) tin(II) chloride h) copper(II) carbonate

i) strontium fluoride j) lead(II) nitrate

Exercise 6

a) iron(III) sulphate b) iron(II) hydroxide

c) copper(II) oxide d) barium sulphate

e) aluminium sulphate f) carbon monoxide

g) sodium chromate h) lead sulphide

i) copper(I) carbonate j) dinitrogen trioxide

k) iron(III) chloride l) zinc phosphate

m) silver(I) iodide n) mercury(II) chloride

o) aluminium nitrate p) magnesium chloride

Exercise 6 (cont.)

q) galium hydroxide r) silver(I) chloride

s) carbon tetrachloride t) calcium carbonate

u) iron(II) carbonate v) argon pentachloride

w) potassium oxide x) sodium hydroxide

y) hydrogen sulphate z) zinc carbonate

aa) hydrogen sulphide

bb) aluminium phosphate

cc) iodine trichloride

dd) barium phosphate

Lesson 6 Compounds with group ions

• We are learning – How to write formulas for compounds

containing group ions

• I can – Write ionic formulae for compounds

containing group ions.

Starter Use valency rules to write the formulae for the following:

a) Nitrogen Hydride

b) Hydrogen oxide

c) Carbon hydride

d) Sodium chloride

e) Boron fluoride

f) Lithium oxide

g) Potassium nitride

h) Aluminium oxide

i) Calcium bromide

j) Sodium phosphide

Starter

Use the VALENCY RULE and the GROUP IONS to work out the ionic formulae for:

(a) calcium phosphate

(b) potassium sulphate

(c) ammonium sulphide

(d) sodium hydrogencarbonate

Chemical Equations

• During a chemical reaction reactants are

turned into new substances called

products. This can be shown by a word

equation where the chemicals reacting are

shown on the left hand side and the

products formed on the right.

Lesson 7: Chemical Equations

• We are learning – To write word equations and chemical

equations to represent the changes in reactants and products for a chemical reaction.

• I can – Write a word equation

– Write a chemical equation

Word Equations

• In a chemical reaction, substances present at the start (reactants) change to make new substances (products):

REACTANTS PRODUCTS

starting substances new substances

reacting produced

e.g. carbon burns in oxygen to become carbon dioxide.

• The starting substances are carbon and oxygen, the new substance formed is carbon dioxide.

• This can be written as a word equation:

• When writing a word equation:

– the ‘+’ means ‘and’

– the means ‘reacts to form’

– the REACTANTS are on the left of the arrow

– the PRODUCTS are on the right of the arrow

Definitions

What is meant by burning(combustion)?

What is meant by decomposing?

Exercise 7

Write each of the following chemical reactions in the form of a word equation:

a) Hydrogen joins up with oxygen to make water

b) Carbon dioxide and water vapour are produced when methane gas reacts with oxygen

c) Iron metal is formed when iron oxide is heated with carbon monoxide, carbon dioxide is also produced

d) In a car engine petrol reacts with oxygen to form carbon dioxide and water vapour

Exercise 7 (cont.)

Write each of the following chemical reactions in the form of a word equation:

e) The reaction of dilute hydrochloric acid with calcium carbonate produces calcium chloride, carbon dioxide and water vapour

f) Silver oxide breaks up when heated to form the elements

g) Ammonium sulphate is a fertiliser produced by the reaction of ammonia with dilute sulphuric acid

Chemical Equations

Exercise 8

Use symbols and formulae to write a chemical equation, with state symbols, for each of the following reactions.

1.carbon monoxide gas + oxygen gas carbon dioxide gas

2.sodium metal + water sodium hydroxide solution + hydrogen gas

3.lead(II) nitrate solution + lead(II) chloride solid +

potassium chloride solution potassium nitrate solution

4.calcium carbonate powder calcium oxide powder + carbon dioxide gas

5.aluminium metal + oxygen gas aluminium oxide solid

Exercise 8 (cont.)

6. iron metal + chlorine gas iron(III) chloride solid

7. magnesium metal + nitric acid (HNO3(aq)) magnesium nitrate solution + hydrogen gas

8. nitrogen gas + hydrogen gas ammonia gas (nitrogen hydride)

9. ammonia gas + sulphuric acid (H2SO4(aq)) ammonium sulphate solution

10. barium chloride solution + barium sulphate solid + sodium sodium sulphate solution chloride solution

Lesson 7: Chemical Equations

• We are learning – To write word equations and chemical

equations to represent the changes in reactants and products for a chemical reaction.

• I can – Write a word equation

– Write a chemical equation

Lesson 8: Balanced Equations

• We are learning – How to balance a chemical equation

• I can – Balance formulae equations so that there

are equal numbers of atoms of each element on both sides of the equations.

Starter Write formula equations for the following reactions:

a) Carbon + oxygen carbon dioxide

b) Sodium + water sodium hydroxide

c) Silver + chlorine silver chloride

d) Ammonia (NH3) nitrogen + hydrogen

e) Magnesium + carbon dioxide magnesium oxide + carbon

Balanced Formulae Equations

Counting Atoms in Compounds 1. NaCl 6. 2CaCO3

2. CO2 7. 3HNO3

3. CH4 8. 2Al2(CO3)3

4. CaCO3 9. 3HPO4

5. Ca(OH)2 10. 2Na2SO4

Balancing Formula Equations • A chemical equation is balanced when there are

equal numbers of each type of atom on both sides of the chemical equation.

• You can only balance equations by putting large numbers in front of the formulae of the reactants and products.

• The formulae cannot be changed (i.e. you cannot add subscript numbers to the formulae.

Three things are balanced in a chemical equation:

1. Atoms

2. Mass

3. Charge

Balanced Equations

Let’s think about some of the reactions we’ve looked at…….

Hydrogen reacts with chlorine to give hydrogen chloride

Hydrogen + Chlorine Hydrogen Chloride

Word equation:

H2+ Cl2 HCl

Formula equation:

BUT: How many atoms have we ‘put in’ to the reaction? How many atoms are ‘coming out’?

Balanced Equations

Hydrogen

Chlorine

Hydrogen Chloride

If using models:

Balanced Equations

Now think back to our formula equation……………….

H2+ Cl2 HCl

Formula equation:

2

Hydrogen

Chlorine

Hydrogen Chloride

H2+ Cl2 HCl

Formula equation:

2

Hydrogen

Chlorine

If using models:

Balanced Equations

Example Hydrogen reacts with chlorine to give hydrogen chloride

Hydrogen + Chlorine Hydrogen Chloride

Word equation:

H2+ Cl2 HCl

Formula equation:

H2+ Cl2 HCl

Balanced equation:

2

When hydrogen burns in oxygen, water is formed. The formula equation for this reaction is:

H2 + O2 H2O

This equation is not balanced.

The same amount of chemicals must be present on both sides of the reaction because atoms cannot be created or destroyed.

H2 + O2 H2O

There are more oxygen atoms on the left hand side than on the right hand side.

ACTIVITY 4.4 Balanced Chemical Reactions

• Try making a molecule each of hydrogen H2

and oxygen O2. Use them to make a molecule

of water H2O.

• The chemical equation for this reaction should

be:

• H2 + O2 → H2O

• But you should find that you have an atom of

oxygen left over. In reality this cannot happen

as we cannot create or destroy matter, so in

order to use up this extra oxygen atom we need

to react it with another hydrogen molecule.

Steps to balance an equation

1. Putting a number in front of formulae multiplies all the atoms after it.

e.g. H2 + O2 H2O

LHS RHS

2 H atoms 4 H atoms

2 O atoms 2 O atoms

2

2. We need to fix the LHS now. Do this by putting a 2 in front of H2 on the LHS.

. H2 + O2 2H2O LHS RHS

4 H atoms 4 H atoms

2 O atoms 2 O atoms

2

More Balancing Equationsc

1.

Mg(s) + O2(g) MgO(s)

2.

Mg(s) + AgNO3(aq) Mg(NO3)2(aq) + Ag(s)

3.

NaOH(aq) + H2SO4 Na2SO4(aq) + H2O(l)

4.

Al(s) + Cl2(g) AlCl3(s)

ACTIVITY 4.5 Balanced

Chemical Equation Activity

Exercise 9

Balance each of the following chemical equations.

1. H2 + Cl2 HCl

2. N2 + O2 NO2

3. Al + Cl2 AlCl3

4. C3H8 + O2 CO2 + H2O

5. H2 + O2 H2O

Exercise 9 (cont.)

6. Ca + H2O Ca(OH)2 + H2

7. Fe2O3 + CO Fe + CO2

8. NH3 + O2 NO + H2O

9. C2H6 + O2 CO2 + H2O

10. NaOH + H2SO4 Na2SO4 + H2O

Lesson 8: Balanced Equations

• We are learning – How to balance a chemical equation

• I can – Balance formulae equations so that there

are equal numbers of atoms of each element on both sides of the equations.

A Chemical Measure

Lesson 9: Calculating Formula Mass

• To calculate formula mass of a substance; given either the name or the formula.

Starter

Balance the following formula equations:

a) C2H4 + O2 CO2 + H2O

b) Ag2S + Al Al2S3 + Ag

c) C6H12O6 + O2 CO2 + H2O

Formula Mass

Relative Atomic Mass (RAM) The mass of an atom is measured on the RELATIVE ATOMIC MASS Scale – and can be found in the Data Book (pg 4). Formula Mass The mass of a compound can be found by adding together the RAM’s of all the atoms in the compound’s formula.

Questions Formula Mass

Example 1: carbon tetrachloride:

Example 2: ammonium carbonate:

Exercise 10

For each of the following substances, calculate the relative formula mass.

1. Na2O 2. NH4OH

3. CuCl2 4. H2

5. SiO2 6. KF

7. Cl2 8. Ca(NO3)2

9. CO2 10. NH4NO3

11. FeCO3 12. Mg(OH)2

13. Si 14. calcium fluoride

15. sulphur trioxide 16. sodium hydride

17. iron(II) hydroxide 18. magnesium sulphide

Starter

Calculate the formula mass of the following substances:

a) CaCl2

b) KBr

c) Na2SO4

d) CH4

e) NH3

Lesson 10 Gram Formula Mass and The Mole

• To understand that the gram formula mass of a substance is the same as the mass of 1 mole of a substance.

• To use the (gram) formula mass of a substance to calculate the number of moles of a substance.

Gram Formula Mass

ONE MOLE is equal to the FORMULA MASS of a substance in GRAMS (or the Gram Formula Mass – GFM). eg The mass of one mole of sodium chloride equals: Two moles of sodium chloride, therefore, has a mass of:

Example 1

• Calculate the mass of 1 mole of carbon tetrachloride.

• The formula mass of CCl4 is :

• So the mass of 1 mole of CCl4 = 154g

Example 2

• Calculate the mass of 1 mole of ammonium carbonate.

• The formula mass of (NH4)2CO3 is :

• So the mass of 1 mole of (NH4)2CO3 = 96g

Example 3

• Calculate the mass of 1 mole of potassium nitrate (KNO3).

• Complete the following calculation:

• So the mass of 1 mole of KNO3 = _________g

Moles to Mass

MASS

GFM n

The relationship between mass, number of moles (n) and relative formula mass (RFM) can be found by using the triangle:

Using the triangle: n = MASS GFM MASS = n x GFM GFM = MASS n

Moles to Mass

Examples: 1. Calculate the mass of 3 moles of sodium oxide

2. Work out the number of moles in 308g of carbon chloride

Exercise 11 (Part 1)

Calculate the mass of one mole of each of the following substances.

1. C 6. sodium oxide

2. Cl2 7. lithium sulphide

3. CO 8. sodium hydroxide

4. MgSO4 9. potassium sulphate

5. (NH4)2CO3 10. ammonium nitrate

Exercise 11 (Part 2)

Calculate the mass of each of the following.

11. 2 mol of C 16. 2.5 mol of carbon dioxide

12. 0.5 mol of MgCl2 17. 1 mol of lithium nitrate

13. 3 mol of CH4 18. 2 mol of oxygen

14. 4 mol of Na2CO3 19. 0.4 mol of potassium carbonate

15. 1.5 mol of Cu2O 20. 0.1 mol of hydrogen sulphide

Exercise 11 (Part 3)

Calculate the number of moles, which are contained in each of the following.

21. 20g of Ca 27. 10.1g of potassium nitrate

22. 54g of H2O 28. 8g of sulphur

23. 12g of He 29. 6.6g of ammonium sulphate

24. 14g of N2 30. a spoonful of sugar (C6H12O6)

25. 10g of CaCO3 weighing 18g

26. 280g of carbon monoxide

Lesson 11: Solutions

• We are learning to

• I can

Concentration & Solutions

The concentration of an aqueous solution is the amount of SOLUTE dissolved in a certain volume of water. In chemistry, the concentration is expressed as: moles of solute dissolved in 1 litre of water

or mol l-1

eg a solution labelled as 1 mol l-1 contains one mole of solute in 1 litre

n

V C

The relationship between number of moles (n), volume (V) and concentration (C) can be found by using the triangle:

Using the triangle: C = n V n = C x V V = n C V must be in litres

Moles, Volume & Concentration

Concentration Calculations

Example 1: Calculate the number of moles of NaCl in 500ml of a solution which has a concentration of 0.1 mol l-1:

Concentration Calculations

Example 2: Calculate the concentration of KOH where 2.5 moles have been dissolved in 2.3 litres of water:

ACTIVITY 4.7 Making

Solutions • Make up the following solutions as

accurately as possible.

• Calculate the concentration of

A. Dissolve 5.85g of sodium chloride in

100cm3 of water.

B. Dissolve 7.2g of sodium chloride in

250cm3 of water.

Example 1: Calculate the concentration of four grams of sodium hydroxide in 600ml water:

Using Two Triangles!

Starter 1. Calculate the mass of 1 mole of:

a) CCl4 b) Mg(NO3)2

2. Calculate the mass of:

a) 1.5 moles of potassium hydroxide

b) 5 moles of magnesium chloride

3. How many moles are present in:

a) 48g of methane (CH4)

b) 6.4g of sulfur dioxide

Starter 1. Write ionic formulae for the following:

a) aluminium hydroxide b) magnesium bromide

c) lithium hydrogencarbonate

2. Calculate the mass of 1 mole of:

a) CaCO3 b) K2SO4

3. How many moles are present in:

a) 16g of oxygen

b) 56g of carbon monoxide

Lesson 12: Calculations from Equations

• To combine our knowledge of formulae, equations and the mole to calculate masses from balanced formulae equations.

Calculations from Balanced Equations

The BALANCED FORMULA EQUATION for a chemical reaction can be used to calculate (i) how much PRODUCT has been made or (ii) how much REACTANT there was at the start This can be done as: TOTAL MASS of REACTANTS = TOTAL MASS of PRODUCTS

Example 1: What mass of water is produced when 8g of hydrogen reacts with oxygen?

Calculations from Balanced Equations

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

Example 2: What mass of CH4 reacts with oxygen to produce 9g of water? (Carbon dioxide is also produced in the reaction).

Calculations from Balanced Equations

CH4(g) + 2O2(g) CO2(g) + 2H2O(l)

Exercise 12 Complete the calculation for each of the following reactions.

1.What mass of water is produced on burning 2g of hydrogen?

2H2 + O2 2H2O

2.What mass of carbon dioxide is produced on burning 4g of methane?

CH4 + 2O2 CO2 + 2H2O

3. What mass of magnesium is required to produce 5g of magnesium oxide?

2Mg + O2 2MgO

4. What mass of ammonia (NH3) is produced from 7g of nitrogen?

N2 + 3H2 2NH3

Exercise 12(cont.)

5. CuO + H2 Cu + H2O

What mass of copper oxide is required to produce 6.8g of copper?

6. C2H4 + 3O2 2CO2 + 2H2O

What mass of water is obtained on burning 4.6g of ethene (C2H4)?

7. C2H4 + H2O C2H5OH (alcohol)

What mass of alcohol is produced from 10kg of ethene?

8. 2SO2 + O2 2SO3

What mass of sulphur dioxide is required to produce 8kg of sulphur trioxide?

Starter

Write the formulae for the following

a) sodium chloride b) potassium bromide

c) calcium carbonate d) magnesium hydroxide

e) ammonium chloride f) lithium sulphate

Lesson 13: Can you make a

profit?

• A small chemical company that has just

developed a new process for turning

vinegar into unleaded petrol. The process

is described below:

• During the process vinegar, which is a solution

of ethanoic acid (CH3CO2H(aq)), is distilled to

separate the ethanoic acid from the water.

• The ethanoic acid is then super heated and

reacted with powdered carbon (C(s)) along

with a special, top secret, catalyst.

• A hydrocarbon similar to petrol (octene, C8H16)

is formed along with carbon dioxide (CO2(g))

as a waste product.

a. Below is the chemical equation for the

reaction, can you balance it.

CH3CO2H(g) + C(s) → CO2(g) + C8H16(l)

b. What mass of petrol (C8H16(l)) will be

produced if 240kg of ethanoic acid reacts

with 48kg of carbon?

c. If Vinegar costs £1.00 per kg, coal costs

£2.00 per kg and running the plant costs £1

per kg of petrol produced; what is the

minimum price the company must sell their

petrol at per kg to make a profit.

d. If 1 litre of petrol weighs roughly 700g can

the business make a profit with today’s

petrol prices?

e. Would you invest in the company?