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1 Dilute sulfuric acid and aqueous potassium hydroxide are used to make aqueous potassium sulfate.
H2SO4 + 2KOH → K2SO4 + 2H2O
The method includes use of the following apparatus.
dilute sulfuric acid
conical flask
25.0 cm3 of aqueous
potassium hydroxide
3
Calculate the volume of 0.0625 mol / dm dilute sulfuric acid, H2SO4, that completely reacts with
3 3
25.0 cm of 0.100 mol / dm potassium hydroxide, KOH, to produce aqueous potassium sulfate.
Use the following steps.
3 3
(a) Calculate the number of moles of KOH in 25.0 cm of 0.100 mol / dm KOH.
= ................................mol [1]
(b) Deduce the number of moles of H2SO4 that react with KOH.
= ................................mol [1]
2
(c) Calculate the volume of H2SO4 required.
3
volume = .................................cm [1]
(d) The experiment is repeated using the same volume and concentration of potassium hydroxide
and the same concentration of dilute sulfuric acid. In this second experiment, the product is
aqueous potassium hydrogensulfate, KHSO4.
H2SO4 + KOH → KHSO4 + H2O
Use your answer to (c) and the equation to deduce the volume of H2SO4 required.
3
volume = .................................cm [1]
[Total: 4]
2 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
Calculate the concentration of NaOH(aq) formed, in g / dm , when 0.345 g of sodium is added to
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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]
3
(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]
3
3 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.
4
3
Determine the concentration of Ca(OH)2 in g / dm . Use the following steps.
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]
5
4 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
5 Determine the volume of CO2 gas given off when excess MgCO3 is added to 25.0 cm of
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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.
................................... mol
• Determine the number of moles of CO2 gas given off.
................................... mol
3
• Calculate the volume of CO2 gas given off in cm .
3
................................... cm [3]
[Total: 3]
6
6 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]
(d) Calculate the volume of nitrogen dioxide formed at room temperature and pressure.
3
........................... dm [1]
[Total: 4]
7 The Avogadro constant is the number of particles in 1 mole.
23
The numerical value of the Avogadro constant is 6.02 x 10 .
7
(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]
8 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]
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(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:
(i) Calculate the mass of 1 mole of ZnCO3.
.......................g [1]
(ii) Calculate the number of moles of ZnCO3 reacting.
...............moles [1]
8
(iii) Determine the number of moles of HNO3 reacting.
...............moles [1]
(iv) Calculate the concentration of HNO3.
3
..........mol / dm [1]
[Total: 6]
