MYP 10 Chemistry 2012-13
Mole Calculations Worksheet
Name: _________________________________ ( )
Class: _________ Date: _____________
_________________________________________________________________________________
The mole concept and Avogadro’s constant
1. Calculate the number of particles in the following amounts of substance.
(a) Carbon atoms in 1.00g of table sugar, C12H22O11
(b) 0.0763 mol sodium chloride formula units, NaCl
[2.11 x 1022, 4.59 x 1022]
2(a) Calculate the amount of nitric acid, HNO3 that contain 9 x 1023 molecules.
(b) Calculate the number of oxygen atoms present in 9 x 1023 molecules of nitric acid.
[1.5, 2.7 x 1024]
3.
(a)
(b)
(c)
(d)
Calculate the mass of :
0.75 mol of NiCl2.2H2O
Al(OH)3 containing 0.02 mol of OH- ions
6.5 dm3 of neon (at r.t.p.)
6.02 x 1023 molecules of S8
4.
(a)
(b)
(c)
Calculate the number of moles of subtsance in each of the following.
75 cm3 of carbon dioxide at rtp.
5.72g of sodium carbonate crystals, Na2CO3.10H2O
ions in 4.0kg of Na2SO4
[124.3g, 0.520g]
[0.00312,0.0200,84.4]
Empirical and molecular formula
5. Determine the empirical formula of a compound containing 85.7% by mass of carbon and 14.3% by
mass of hydrogen.
6. Analysis of a 8.456g sample of a silicon-chlorine compound shows that it contains 6.519g of chlorine.
Calculate the empirical formula of the compound.
7. Ascorbic acid (vitamin C) is an organic compound containing carbon , hydrogen and oxygen. When
1.000g of ascorbic acid was completely burnt in oxygen, 1.500g of carbon dioxide and 0.405g of water
were formed. Calculate the empirical formula of ascorbic acid.
[C3H4O3]
8. A compound contains 73.47% carbon, 10.20% hydrogen and 16.33% by mass of oxygen. The
compound has a molar mass of 196 gmol-1. Calculate the molecular formula.
[C12H20O2]
9. 2.40g of an organic compound consisting of carbon, hydrogen and oxygen only gave, on combustion,
3.52g of carbon dioxide and 1.44g of water. The relative molecular mass of the compound was found to
be 60.0. What are the emipirical and molecular formulae of the compound?
10. An iron-containing protein has a molar mass of 136 000gmol-1. 0.33% by mass is iron. Calculate the
number of iron atoms present in one molecule of the protein.
[8]
11. Calculate the percentage composition by mass of
(a) methane, CH4.
(b) hydrated sodium sulfate,Na2SO4.10H2O
[75%C,25%H]
[14.3%Na,9.9%S,19.9%O, 55.9% water]
12.
*12. Bones contain a complex mixture of calcium salts, protein and other material. When a bone is strongly
heated in a current of air, the only residue is calcium oxide. From a sample of 50.0 g of bone, 14.0g of
calcium oxide were obtained. What is the percentage by mass of calcium in the bone?
Theoretial yield
13. Calculate the mass of calcium carbonate that coud be obtained by heating 2.5 grams of calcium
carbonate CaCO3. (Assume that the calcium carbonate is pure and that complete decomposition occurs).
[1.4g]
*14. Calculate the mass of nitric acid that can be produced from 56 grams of nitrogen gas.
N2 + 3H2  2NH3
4NH3 + 5O2  4NO + 6H2O
2NO + O2  2NO2
2H2O + 4NO2  4HNO3
[252g]
The limiting reactant and the reactant in excess
15. Calculate the mass of magnesiun that can be obtained from the reaction between 4.8 grams of
magnesium and 4.8 grams of sulfur. Identify the limiting reactant and calcualte the mass of the
unreacted element present in excess.
[8.4g,sulfur is the LR, 1.2g]
16. 0.600 mol of aluminium hydroxide is mixed with 0.600 mol of sulfuric acid, and the following reaction
occurs:
2Al(OH)3 (s) + 3H2SO4 (aq)  Al2(SO4)3 (aq) + 6H2O(l)
(a) Determine the limiting reactant.
(b) Calculate the mass of Al2(SO4)3 produced.
(c) Determine the amount(in mol) of the excess reactant that remains.
[(b)68.4g(c)0.200mol]
17 . Calcium and hydrochloric acid react according to the equation:
Ca(s) + 2HCl(aq)  CaCl2(aq) + H2(g)
(a) 0.122g of calcium metal was added to 25.0cm3 of 1.23 mol dm-3 solution of hydrochlroic acid and teh
hydrogen gas was collected at room temperature and pressure.
(i) Calculate whether the calcium or hydrochloric acid was in excess.
(ii) Hence calculate the volume of hydrogen gas produced.
[HCl, 73.2cm3]
18(a) Write an equation for the formation of zinc iodide from zinc and iodine.
(b) 100.0g of zinc is allowed to react with 100.0g of iodine producing zinc iodide. Calculate the
amount (in moles) of zinc and iodine, and hence determine which reactant is in excess.
(c) Calculate the mass of zinc iodide that will be produced.
[HL paper 2, May 04]
[(b)Zn:1.530mol,I2:0.3940mol(c)125.8g]
Percentage and experimental yield
19. In an experiment to produce a sample of hex-1-ene, 20.4 grams of hexan-1-ol was heated with an excess
of phosphoric(V) acid. The phosphoric(V) acid acted as a dehydrating agent, removing water from the
alcohol to form hex-1-ene.
CH3CH2 CH2 CH2 CH2 CH2OH  CH3CH2 CH2 CH2 CH=CH2 + H2O
hexan-1-ol
hex-1-ene
After purification of the hex-1-ene, 10.08 grams was produced. Calculate the percentage yield.
[60%]
20. Aspirin, C9H8O4, is made by reacting ethanoic anhydride, C4H6O3 (Mr = 102.1), with 2-hydroxybenzoic
acid (Mr = 138.1), according to the equation:
2C7H6O3 + C4H6O3  2C9H8O4 + H2O
(a) If 15.0g of 2-hydroxybenzoic acid is reacted with 15.0 g ethanoic anhydride, determine the limiting
reagent in this reaction.
(b) Calculate the maximum mass of aspirin that could be obtained in this reaction.
(c) If the mass obtained in this experiment was 13.7g, calculate the percentage yield of aspirin.
[(b) 19.6g (c)69.9%]
Percentage purity
21. When 12 grams of impure carbon was burnt in excess oxygen, 33 grams of carbon dioxide was obtained.
Calculate the percentage purity of the carbon.
[75%]
22. A 1.00 g sample of impure ammonium sulfate was heated with excess sodium hydroxide. Ammonia gas
and water were produced. The ammonia liberated was absorbed by 50.0 cm3 of 2.00 mol/dm3
hydrochloric acid.
(a) Write a balanced equation for the formation of ammonia.
(b) Calculate the number of moles of ammonia liberated.
(c) Write a balanced equation for the formation of ammonia.
(d) Calculate the mass of ammonium sulfate in the sample.
(e) Calculate the percentage purity of ammonium sulfate in the sample.