Moles Past Paper Questions Homework
1) A solution was made by dissolving 117g of sodium chloride in 250 cm3 of water
a. Calculate the relative formula mass of sodium chloride
b. Calculate the amount in moles in the 117g sample
c. Calculate the concentration in mol dm-3 of the sodium chloride solution
d. Calculate the concentration in g dm-3 of the sodium chloride solution
2) One reaction that occurs in the blast furnace during the extraction of iron is the
reaction between iron(III)oxide and carbon.
Fe2O3 + 3C  2Fe + 3CO
a) Calculate the relative formula mass of iron(III) oxide, using information from the
Periodic Table.
320 kg of iron(III) oxide were added to the blast furnace.
b) Calculate the amount, in moles, of iron(III) oxide added.
c) Calculate the maximum amount, in moles, of iron formed from this amount of
iron(III) oxide.
d) Calculate the maximum mass, in kilograms, of iron formed from this amount of
iron(III) oxide.
e) During one period in the operation of the blast furnace, the amount of carbon
dioxide released was 5000 moles.
Calculate the volume, in dm3, that this amount of carbon dioxide would occupy
at room temperature and pressure (rtp).
(The molar volume of a gas is 24 dm3 at rtp.)
3) A student wanted to find the concentration of a solution of nitric acid.
She placed a 25.0 cm3 sample of the nitric acid solution in a conical flask and titrated it with
0.200 mol dm–3 sodium hydroxide solution, using phenolphthalein as an indicator. The
phenolphthalein changed colour after she added a total of 21.05 cm3 of the sodium hydroxide
solution.
The equation for the reaction is:
NaOH(aq) + HNO3(aq)  NaNO3(aq) + H2O(l)
a)
b)
c)
d)
Calculate the amount, in moles, of sodium hydroxide used in the titration.
Calculate the concentration, in mol dm–3, of the nitric acid.
Calculate the relative formula mass of sodium nitrate.
Calculate the mass of sodium nitrate formed in the titration.
Moles Past Paper Questions
1. Much of the sulphur dioxide required for the manufacture of sulphuric acid is
obtained from roasting metal sulphide ores such as zinc sulphide in air. The
equation for this reaction is:
2ZnS + 3O2 → 2ZnO + 2SO2
a) Calculate the maximum volume of sulphur dioxide, measured at room temperature
and atmospheric pressure, which would be released when 48.5 kg of zinc sulphide is
roasted. (Relative atomic masses: Zn = 65, S = 32)
In the next stage of the process, the sulphur dioxide is converted into sulphur
trioxide.
2SO2 + O2 → 2SO3
b) What volume of sulphur trioxide, measured under the same conditions, is obtained
from 1000 dm3 of sulphur dioxide?
c) What volume of oxygen, measured under the same conditions, would be used?
2) A student made a solution of potassium hydroxide by dissolving 14.0 g of solid
potassium hydroxide in distilled water to make 250 cm3 of solution.
a) Calculate the relative formula mass of potassium hydroxide, KOH.
b) Calculate the amount, in moles, of potassium hydroxide in 14.0 g.
c) Calculate the concentration, in mol dm–3, of this solution of potassium hydroxide.
Show your working.
A different solution of potassium hydroxide, of concentration 2.0 mol dm–3, was
used in an experiment to react with carbon dioxide gas. The equation for this
reaction is:
2KOH(aq) + CO2(g) → K2CO3(aq) + H2O(l)
d) Calculate the amount, in moles, of potassium hydroxide in 200 cm3 of this solution.
e) Calculate the amount, in moles, of carbon dioxide that reacts with 200 cm3 of this
solution of potassium hydroxide.
f) Calculate the volume that this amount of carbon dioxide occupies at room
temperature and pressure (rtp).
The concentration of a solution of sodium hydroxide was found by titrating the solution
with 0.200 mol dm–3 sulphuric acid.25.0 cm3 of the sodium hydroxide solution required
31.5 cm3 of the sulphuric acid for complete reaction. The equation for the reaction is
2NaOH + H2SO4 → Na2SO4 + 2H2O
1. Calculate the concentration, in mol dm–3, of sodium hydroxide in the solution.
2. Calculate the concentration, in g dm–3, of sodium hydroxide in the solution.