1
1 A compound of copper has the formula K2CuF4.
Complete the table to calculate the relative molecular mass of K2CuF4.
number relative
atom
of atoms atomic mass
potassium 2 39 2 x 39 = 78
copper 64
fluorine 19
relative molecular mass = ................. [2]
[Total: 2]
2 A student prepares magnesium sulfate crystals, MgSO4, by adding excess magnesium to dilute
sulfuric acid.
Write the chemical equation for this reaction.
.................................................................................................................................................. [1]
[Total: 1]
3 A compound of chromium has the formula CrH2O6.
Complete the table to calculate the relative molecular mass of CrH2O6.
number relative
atom
of atoms atomic mass
chromium 1 52 1 x 52 = 52
hydrogen 1
oxygen 16
relative molecular mass = ............................... [2]
[Total: 2]
4 The table compares the percentage by mass of the elements in the Earth’s crust and in the Moon’s
crust.
percentage by mass percentage by mass
element
in the Earth’s crust in the Moon’s crust
aluminium 8.20 7.50
calcium 3.60 7.50
2
iron 5.00 13.50
magnesium 2.00 5.50
oxygen 46.60 40.00
silicon 29.50 19.50
titanium 0.55 3.00
other elements 4.55
total 100.00 100.00
Answer these questions using only the information in the table.
(a) Deduce the percentage by mass of the other elements in the Moon’s crust.
........................................................................................................................................... [1]
(b) State which element is present in the Earth’s crust in the greatest percentage by mass.
........................................................................................................................................... [1]
(c) Give two major differences in the composition of the Earth’s crust and in the Moon’s crust.
1 ........................................................................................................................................
...........................................................................................................................................
2 ........................................................................................................................................
........................................................................................................................................... [2]
[Total: 4]
5 Phosphorus oxychloride has the formula POCl3.
Phosphorus oxychloride is the only product of the reaction between phosphorus(V) chloride, PCl5,
and phosphorus(V) oxide, P4O10.
Write a chemical equation for the reaction between phosphorus(V) chloride and
phosphorus(V) oxide.
.................................................................................................................................................. [2]
[Total: 2]
6 Sodium reacts vigorously with water to form aqueous sodium hydroxide, NaOH, which is a strong
base.
The equation for the reaction is shown.
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g)
3
3
Calculate the concentration of NaOH(aq) formed, in g / dm , when 0.345 g of sodium is added to
3
50.0 cm of distilled water. Assume there is no change in volume.
Use the following steps.
(a) Calculate the number of moles of Na added.
= ............................... mol [1]
(b) Determine the number of moles of NaOH formed.
= ............................... mol [1]
3
(c) Calculate the concentration of NaOH in mol / dm .
3
concentration of NaOH = .......................... mol / dm [1]
3
(d) Determine the Mr of NaOH and calculate the concentration of NaOH in g / dm .
3
concentration of NaOH = .............................. g / dm [2]
[Total: 5]
4
7 Compound Y has the empirical formula H3PO4 and a relative molecular mass of 98.
Deduce the molecular formula of compound Y.
molecular formula = .......................... [1]
[Total: 1]
8 Ester Y has the following composition by mass:
C, 58.82%; H, 9.80%; O, 31.37%.
Calculate the empirical formula of ester Y.
empirical formula = ........................... [3]
[Total: 3]
9 The formula for crystals of hydrated copper(II) sulfate is CuSO4•5H2O.
Hydrated copper(II) sulfate is made by reacting copper(II) oxide with dilute sulfuric acid.
The overall equation is shown.
CuO + H2SO4 + 4H2O → CuSO4•5H2O
The crystals are made using the following steps:
3 3
step 1 50.0 cm of 0.200 mol / dm dilute sulfuric acid is heated in a beaker. Powdered copper(II)
oxide is added until the copper(II) oxide is in excess. Aqueous copper(II) sulfate is formed.
step 2 The excess copper(II) oxide is separated from the aqueous copper(II) sulfate.
step 3 The aqueous copper(II) sulfate is heated until a saturated solution is formed.
step 4 The saturated solution is allowed to cool and crystallise.
step 5 The crystals are removed and dried.
5
Calculate the maximum mass of copper(II) sulfate crystals, CuSO4•5H2O, that can form using the
following steps.
3 3
(a) Calculate the number of moles of H2SO4 in 50.0 cm of 0.200 mol / dm H2SO4.
...................................mol [1]
(b) Deduce the number of moles of CuSO4•5H2O that can form.
...................................mol [1]
(c) The Mr of CuSO4•5H2O is 250.
Calculate the maximum mass of CuSO4•5H2O that can form.
.......................................... [1]
[Total: 3]
6
10 A student determines the concentration of a solution of dilute sulfuric acid, H2SO4, by titration with
aqueous sodium hydroxide, NaOH.
The equation for the reaction is shown.
H2SO4 + 2NaOH → Na2SO4 + 2H2O
Calculate the concentration of H2SO4 using the following steps.
3 3
• Calculate the number of moles in 25.0 cm of 0.200 mol / dm NaOH.
.................................... m o l
• Determine the number of moles of H2SO4 that react with the NaOH.
.................................... m o l
• Calculate the concentration of H2SO4.
3
............................ mol / dm [3]
[Total: 3]
7
11 Ester Y has the following composition by mass:
C, 48.65%; H, 8.11%; O, 43.24%.
Calculate the empirical formula of ester Y.
empirical formula = ........................................ [3]
[Total: 3]
3
12 A 25.0 cm sample of limewater is placed in a conical flask.
The concentration of Ca(OH)2 in the limewater is determined by titration with dilute hydrochloric
acid, HCl.
(a) Name the item of apparatus used to measure the volume of acid in this titration.
........................................................................................................................................... [1]
(b) State the type of reaction which takes place.
........................................................................................................................................... [1]
(c) As well as limewater and dilute hydrochloric acid, state what other type of substance must be
added to the conical flask.
........................................................................................................................................... [1]
(d) The equation for the reaction is shown.
Ca(OH)2 + 2HCl → CaCl2 + 2H2O
3 3 3
20.0 cm of 0.0500 mol / dm HCll reacts with the 25.0 cm of Ca(OH)2.
3
Determine the concentration of Ca(OH)2 in g / dm . Use the following steps.
8
3 3
(i) Calculate the number of moles in 20.0 cm of 0.0500 mol / dm HCl.
.............................................mol [1]
3
(ii) Determine the number of moles of Ca(OH)2 in 25.0 cm of the limewater.
.............................................mol [1]
3
(iii) Calculate the concentration of Ca(OH)2 in mol / dm .
3
.....................................mol / dm [1]
3
(iv) Determine the concentration of Ca(OH)2 in g / dm .
3
........................................g / dm [2]
[Total: 8]
9
13 Fluorine reacts with sulfur to form a compound which has 25.2% sulfur by mass and a relative
molecular mass of 254.
Determine the molecular formula of this compound.
molecular formula = ......................................... [3]
[Total: 3]
3
14 Determine the volume of CO2 gas given off when excess MgCO3 is added to 25.0 cm of
3
0.400 mol / dm HCl at room temperature and pressure.
MgCO3 + 2HCl → MgCl2 + H2O + CO2
Use the following steps.
3 3
• Calculate the number of moles of HCl in 25.0 cm of 0.400 mol / dm of acid.
.................................... m o l
• Determine the number of moles of CO2 gas given off.
.................................... m o l
3
• Calculate the volume of CO2 gas given off in cm .
3
.................................... cm [3]
[Total: 3]
10
15 135 moles of urea, (NH2)2CO, is stored in the tank of a car.
Calculate the mass, in kg, of the stored (NH2)2CO.
mass of (NH2)2CO = .................................. kg [2]
[Total: 2]
16 When solid copper(II) nitrate is heated copper(II) oxide, nitrogen dioxide and oxygen are formed.
2Cu(NO3)2 → 2CuO + 4NO2 + O2
Calculate the volume of nitrogen dioxide formed at room temperature and pressure when 4.7 g of
Cu(NO3)2 is heated.
Use the following steps:
(a) Calculate the mass of one mole of Cu(NO3)2.
............................... g [1]
(b) Calculate the number of moles of Cu(NO3)2 used.
........................ moles [1]
(c) Determine the number of moles of nitrogen dioxide formed.
........................ moles [1]
11
(d) Calculate the volume of nitrogen dioxide formed at room temperature and pressure.
3
........................... dm [1]
[Total: 4]
17 The Avogadro constant is the number of particles in 1 mole.
23
The numerical value of the Avogadro constant is 6.02 x 10 .
(a) Calculate the number of molecules in 22.0 g of carbon dioxide, CO2.
.......................................molecules [2]
3
(b) Calculate the number of molecules in 6.00 dm of carbon dioxide gas at room temperature
and pressure.
.......................................molecules [1]
[Total: 3]
18 The equation for the reaction between powdered zinc carbonate and dilute nitric acid is shown.
(a) ZnCO3............ + 2HNO3............ → Zn(NO3)2............ + H2O............ + CO2............
Complete the equation by adding state symbols. [2]
3
(b) A student found that 2.5 g of zinc carbonate required 20 cm of dilute nitric acid to react
completely.
Calculate the concentration of dilute nitric acid using the following steps:
12
(i) Calculate the mass of 1 mole of ZnCO3.
.......................g [1]
(ii) Calculate the number of moles of ZnCO3 reacting.
...............moles [1]
(iii) Determine the number of moles of HNO3 reacting.
...............moles [1]
(iv) Calculate the concentration of HNO3.
3
...........mol / dm [1]
[Total: 6]
