Mole Calculations
Case 1:
1. 200 g of pure calcium carbonate are heated strongly. Calculate:
The mass of calcium oxide and volume of carbon dioxide produced.
CaCO3
CaO + CO2
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2. Calculate the volume of 1 mol/dm3 solution of H2SO4 required to
react with 6g of Mg, and the volume of H2 produced at r.t.p.
Mg + H2SO4
MgSO4 + H2
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3. Calculate the volume of methane needed to react with 70 dm3 of
oxygen.
CH4 + 2 O2
CO2 + 2 H2O
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a) The volume of carbon dioxide produced at r.t.p.
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Case 2 :
1. 3 g of magnesium was added to 12.0 g of ethanoic acid Mg + 2
CH3COOH
(CH3COO)2 Mg +H2
The mass of one mole of Mg is 24 g.
The mass of one mole of acid is 60 g.
Which one, magnesium or ethanoic acid, is an excess? Show your
work.
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(a) How many moles of hydrogen were formed?
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(b) Calculate the volume of hydrogen formed measured at r.t.p.?
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2. Calculate the mass of FeS produced from the reaction between
28g of iron with 20g of sulfur
Fe + S
FeS
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Percentage purity and percentage yield:
1. When 10 g of impure zinc reacted with dilute H2SO4, 2.4 dm3
of hydrogen gas ware collected at r.t.p. Calculate the
percentage purity of zinc?
Zn + H2SO4
ZnSO4 + H2
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2. Heating 12.4 g of copper (II) carbonate produced only 7 g of
copper (II) oxide. What is the % yield of copper oxide?
CuCO3
CuO + CO2
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Percentage composition of element in a compound:
1. Find the % composition of nitrogen In the following
(a) Ammonium nitrate
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(b) Ammonium sulfate
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Empirical & molecular formulae:
1. A hydrocarbon contains 80 % carbon. Find the empirical formula
and the molecular formula, if the Mr of the compound is 30.
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2. Calculate the empirical formula of the formed compound from the
reaction of 0.24g Mg with 0.16g oxygen.
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3. 4.2g of cerium reacted with oxygen to form 5.16g of an oxide of
cerium. Complete the following to determine the formula of this
oxide.
• Number of moles of cerium atoms used
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• Mass of oxygen that reacted ………………………………………..g
• Number of moles of oxygen atoms in oxide……………………
• Ratio by moles of cerium atoms to oxygen atoms …………..
• Formula of the oxide of cerium is……………………………………..
4. An excess of hydrochloric acid was added to 1.23g of barium
carbonate. The volume of carbon dioxide collected at r.t.p. was
0.120dm3. The impurities did not react with the acid. Calculate
the percentage purity of the barium carbonate. BaCO3 + 2HCl →
BaCl2 + CO2 + H2O Molar gas volume at r.t.p. is 24 dm3.
(i) The numbers of moles of CO2 collected ………………… …………mole
(ii) The numbers of moles of BaCO3 reacted …………………mole
(iii) Mass of mole of BaCO3…….…………………………………………..g
(iv) Mass of barium carbonate ……………………………………………g
(v) Percentage purity of barium carbonate ……………………..…
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