1. No category

Lesson 08
PCY102A STOICHIOMETRY & ORGANIC CHEM
Page |1
Worksheet – More Stoichiometry
For Q1-3 below, select the correct answer from the options given.
1. Magnesium reacts with oxygen according to the balanced equation:
2Mg (s) + O2 (g) → 2MgO (s)
In this reaction :
(a) 2 g of magnesium will react with 1 g of oxygen to produce 2 g of magnesium oxide
(b) 2 g of magnesium will react with exactly 1 g of oxygen
(c) 2 moles of magnesium are needed for every mole of oxygen used
(d) 2 moles of oxygen are needed for every mole of magnesium used.
2. Sodium thiosulfate, Na2S2O3 known as 'hypo' by photographers, is used to remove
excess silver bromide , AgBr, in the film-developing process according to the balanced
equation:
2Na2S2O3 (aq) + AgBr (s) → Na3Ag(S2O3)2 (aq) + NaBr (aq)
In the equation for the reaction between sodium thiosulfate and silver bromide:
(a) 1 mole of sodium thiosulfate solution will produce 1 mole of sodium bromide
(b) 3 moles of sodium thiosulfate solution will produce 2 moles of Na3Ag(S2O3)2
(c) 1 mole of sodium thiosulfate solution will produce two moles of sodium bromide
(d) 1 mole of silver bromide will produce 1 mole of Na3Ag(S2O3)2
3. The combustion of propane in air is represented by the equation:
HINT: convert the
C3H8 (g) + 5O2 (g) → 3CO2 (g) + 4H2O (g)
mass into moles
To produce 44 g of carbon dioxide in this reaction:
(a) one-third of a mole of propane will react with five-thirds of a mole of oxygen
(b) 1 mole of propane will react with 1 mole of oxygen
(c) 1 mole of propane will react with 5 moles of oxygen
(d) 3 moles of propane will react with 15 moles of oxygen.
4. Nitrogen in the cylinder of a car reacts with oxygen to produce the pollutant nitrogen
monoxide…
N2 (g) + O2 (g) → 2NO (g)
(a) How many moles of nitrogen are needed to produce 1.52 mol nitrogen monoxide?
(b) How many grams of oxygen are needed for this reaction?
Lesson 08
PCY102A STOICHIOMETRY & ORGANIC CHEM
Page |2
Worksheet – More Stoichiometry
5. Balance the equations and then determine the number of moles of each chemical which
reacts or is produced.
(a)
__ N2 (g) + __ CI2 (g) → __ NCI3 (l)
n (N2)
(i)
(ii)
(iii)
(b)
n (Cl2)
n (NCl3)
6.0 mol
4.0 mol
4.0 mol
3.2 mol
__ C2H8 (g) + __ O2 (g) → __ CO2 (g) + __ H2O (l)
n (C2H8)
(i)
n (CO2)
n (H2O)
0.3 mol
(ii)
(iii)
n (O2)
4.0 mol
6.0 mol
6. When sodium and chlorine are reacted, table salt is produced.
(a) Write the balanced equation for the reaction.
(b) If 10 g of sodium were used, how much table salt would be produced?
7. It has been estimated that 4.0 x 109 tonnes of oxygen are produced annually by
photosynthesis in plants to produce glucose…
6CO2 (g) + 6H2O (I) → C6H12O6 (s) + 6O2 (g)
(a) What mass of carbon dioxide is consumed in producing this amount of oxygen?
(b) What mass of glucose is formed?
JAMES, M. et al (1999)
Chemical Connections 1
3rd ed. John Wiley & Sons
Australia Ltd.
pp.290-293
Lesson 08
PCY102A STOICHIOMETRY & ORGANIC CHEM
Page |3
Solutions – More Stoichiometry
1.(c)
2.(d)
3.(a)
4.(a) 0.760 mol (b) 24.3 g
5.(a) N2 (g) + 3CI2 (g) → 2NCl3 (l)
(i) 2.0 mol N2 (ii) 12 mol Cl2; 8 mol NCl3 (iii) 9.6 mol Cl2; 6.4 mol NCl3
5.(b) C2H8 (g) + 4O2 (g) → 2CO2 (g) + 4H2O (I)
(i) 0.075 mol C2H8; 0.15 mol CO2; 0.30 mol H2O
(ii) 2.00 mol C2H8; 8.00 mol O2; 8.00 mol H2O
(iii) 24.0 mol O2; 12.0 mol CO2; 24.0 mol H2O
6. (a) 2Na (s) + CI2 (g) → 2NaCI (s) (b) 25 g
7. (a) 5.5 x 109 tonnes (b) 3.8 x 109 tonnes