141
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?
