Chemical equations
1. Iron can be obtained from the compound iron (II) oxide by reducing the oxide with
hydrogen gas. The equation for this reaction is shown below:
FeO + H2 → Fe + H2O
What mass of iron will be produced when hydrogen gas is reacted with 6 g of iron (II)
oxide?
Fe = 56, H = 1, O = 16
2. Sodium chloride, NaCl, can be formed by reacting sodium metal with chlorine gas.
The balanced chemical equation for the reaction is shown below:
2Na + Cl2 → 2NaCl
What mass of sodium chloride is formed from 11.5 g of sodium metal?
Na = 23, Cl = 35.5
3. Lithium oxide, Li2O reacts with water to form lithium hydroxide, LiOH. The balanced
equation for this reaction is shown below:
LiO + H2O → 2LiOH
What mass of lithium hydroxide is obtained when 15 g of lithium oxide is reacted
with excess water?
Li = 7, O = 16, H = 1 4.
4. When a piece of solid copper was heated in a Bunsen flame, a thin black layer of
copper (II) oxide, CuO formed on the surface. The unbalanced chemical reaction is
shown below:
__ Cu + O2 → __ CuO
a. Balance the above equation for this reaction.
b. Calculate the mass of copper (II) oxide formed
when 10 g of copper was heated.
Cu = 63.5, O = 16
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Chemical equations
5. The metal calcium reacts with hydrochloric acid to form the salt calcium chloride,
CaCl2. The unbalanced chemical reaction is shown below:
Ca + __ HCl → CaCl2 + H2
a. Balance the above chemical reaction.
b. How many moles of hydrochloric acid, HCl are required to react with 20 g of
calcium metal.
c. What mass of calcium chloride salt is formed when excess acid is reacted with
20 g of calcium?
Ca = 40, Cl = 35.5, H = 1
6. Aluminium oxide can be reacted with sodium hydroxide solution to produce the
important industrial chemical sodium aluminate, NaAlO2. The unbalanced chemical
equation is shown below:
Al2O3 + __ NaOH → __ NaAlO2 + H2O
a. Balance the above equation for this reaction.
b. What mass of sodium aluminate, NaAlO2 will be produced when100 g of
aluminium oxide, Al2O3 is reacted with excess sodium hydroxide solution?
c. How many tonnes of sodium aluminate are produced for each tonne of
aluminium oxide reacted with excess sodium hydroxide solution?
Al = 27, Na = 23, O = 16, H = 1
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Chemical equations
Answers
1.
6
72
𝑚𝑎𝑠𝑠 𝑜𝑓 𝐹𝑒
56
=
𝑚𝑎𝑠𝑠 𝑜𝑓 𝐹𝑒 = 4.67 𝑔
2.
11.5
2 ×23
3.
15
30
=
=
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑁𝑎𝐶𝑙
2 ×58.5
𝑚𝑎𝑠𝑠 𝑜𝑓 𝐿𝑖𝑂𝐻
2 ×24
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑁𝑎𝐶𝑙 = 29.3 𝑔
𝑚𝑎𝑠𝑠 𝑜𝑓 𝐿𝑖𝑂𝐻 = 24 𝑔
4.
a. Balanced equation 2Cu + O2 → 2CuO
b.
10
2 ×63.5
=
𝑚𝑎𝑠𝑠 𝑜𝑓 𝐶𝑢𝑂
2 ×79.5
𝑚𝑎𝑠𝑠 𝑜𝑓 𝐶𝑢𝑂 = 12.5 𝑔
5.
a. Ca + 2HCl → CaCl2 + H2
b. 20 g of calcium equals 0.5 mol, thus 1 mole of HCl is required
c.
20
40
=
𝑚𝑎𝑠𝑠 𝑜𝑓 𝐶𝑎𝐶𝑙2
111
𝑚𝑎𝑠𝑠 𝑜𝑓 𝐶𝑎𝐶𝑙2 = 55.5 𝑔
6.
a. Balanced equation Al2O3 + 2NaOH → 2NaAlO2 + H2O
b.
100
102
=
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑁𝑎𝐴𝑙𝑂2
2 ×82
𝑚𝑎𝑠𝑠 𝑜𝑓 𝑁𝑎𝐴𝑙𝑂2 = 160.8 𝑔
c. 1.6 tonnes formed from each tonne of sodium aluminate
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