TOPIC:MOLE CONCEPT
Name: _____________________________
Class: O level
Subject: Chemistry
Teacher: Ayesha Sharmin
Full Marks: 40
Marks Obtained:
Duration: 1hour
Date: 22.10.19
1.In an experiment to find the number of molecules of water of crystallization in sodium sulphate crystals,
Na2SO4.nH2O,3.22 g of sodium sulphate crystals were heated gently. When all the water of crystallization
had been driven off,1.42g of anhydrous sodium sulphate was left. Find the value for n in the formula.
(4 marks)
2. How many water molecules, H2O, are there in one drop of water? Assume one drop of water is 0.05cm3,
and that the density of water is 1gcm-3.
(2 marks)
1
3.Calcium hydroxide is manufactured by heating calcium carbonate strongly to produce calcium oxide and
then adding a controlled amount of water to produce calcium hydroxide.
CaCO3(s)→CaO(s)+CO2(g)
CaO(s)+H2O(l)→Ca(OH)2(s)
(a) What mass of calcium oxide would you produce from 1 tonne of calcium carbonate? (2)
(b) What mass of water would you need to add to that calcium oxide? (2)
(c) What mass of calcium hydroxide would you eventually produce? (2)
(Total 6 marks)
4.Calculate the volume of hydrogen (measured at room temperature and pressure) which can obtained by
reacting 0.240g of magnesium with an excess of dilute sulphuric acid.(Molar volume=24000cm3 at rtp).
Mg(s) + H2SO4(aq) → MgSO4(aq) + H2(g)
(3marks)
2
5.Copper(ll)sulphate crystals, CuSO4.5H2O, can be made by heating copper(ll) oxide with dilute sulphuric
acid and then crystallising the solution formed.
(a) Calculate the maximum mass of crystals that could be made from 4.00g of copper(ll)oxide using an
excess of sulfuric acid.
CuO(s)+H2SO4(aq)
→ CuSO4(aq)+H2O(l)
CuSO4(aq)+5H2O(l) → CuSO4.5H2O(s)
(3marks)
(b) If the actual mass of copper(ll) sulphate collected at the end of the experiment was11.25g, calculate the
percentage yield.
(2marks)
6.Chlorine can be prepared by heating manganese(lV) oxide with an excess of concentrated hydrochloric
acid.What is the maximum volume of chlorine(measured at room temperature and pressure) that could be
obtained from 2.00g of manganese(IV)oxide?
(3marks)
MnO2(s)+4HCl→MnCl2(aq)+Cl2(g)+2H2O(l)
3
7.Titanium is manufactured by heating titanium(IV)chloride with sodium
TiCl4(g)+4Na(l)→Ti(s)+4NaCl(s)
What mass of sodium is required to produce 1 tonne of titanium?
(2marks)
8. What volume of ammonia gas will be produced in the following reaction if 50cm3 of 0.5moldm-3
Sodium hydroxide is boiled with 50cm3 of 0.4moldm-3 ammonium chloride solution?
NaOH(aq)+NH4CI(aq)
→
(4 marks)
NaCI(aq)+H2O(I)+NH3(g)
9. When excess carbon dioxide is passed into sodium hydroxide solution,sodium carbonate solution is
formed.This can be crystallised out asNa2CO3.10H2O.What mass of crystals would be produced from 5g of
sodium hydroxide in excess water.
(3 marks)
2NaOH(aq)+CO2(g)+9H2O → Na2CO3(aq)+10H2O(I) →
Na2CO3.10H2O(s)
4
10.When 1.335g of a chloride of aluminium is added to excess silver nitrate solution 4.305g of silver
chloride is produced.Calculate the empirical formula of the chloride of aluminium.
(4 marks)
11. 16g of hydrocarbon burn in excess oxygen to produce 44g of carbon dioxide.What is the empirical
formula of the hydrocarbon.
(4 marks)
THE END
5