Name:
Class:
2020-2021 ACADEMIC YEAR
No:
11th Grade
Date: 13/09/2020
IB CHEMISTRY
STOICHIOMETRY-1
HOMEWORK 5
1. 0.5438 g sample of a compound known to contain only carbon, hydrogen, and oxygen was burned
completely in oxygen. The products were 1.0390 g CO2 and 0.6369 g H2O. Determine the empirical formula
of the compound.
2. Nitrogen gas, N2, can be prepared from this reaction: 2NH3(g) + 3CuO(s) → N2(g) + 3Cu(s) + 3H2O(g) If
18.1 g NH3 are reacted with 90.40 g CuO, determine the mass of N2 that can be formed?
3. The previous question on the synthesis of N2 from NH3 and CuO had a theoretical yield of 10.7 g N2 from
the starting amounts of reactants. Under the same conditions, an experiment produced 8.35 g N2.
Determine the percentage yield.
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4. Iron ore can be reduced to iron by the following reaction: Fe2O3(s) + 3H2(g) → 2Fe + 3H2O(l)
(a) How many moles of Fe can be made from 1.25 moles of Fe2O3?
(b) How many moles of H2 are needed to make 3.75 moles of Fe?
(c) If the reaction yields 12.50 moles of H2O, what mass of Fe2O3 was used up?
5. Lighters commonly use butane, C4H10, as the fuel.
(a) Formulate the equation for the combustion of butane.
(b) Determine the mass of butane that burned when 2.46 g water were produced.
6. Booster rockets for the space shuttle use the following reaction: 3Al(s) + 3NH4ClO4(s) → Al2O3(s) + AlCl3(s)
+ 3NO(g) + 6H2O(g) Calculate the mass of NH4ClO4 that should be added to this fuel mixture to react
completely with every kilogram of Al.
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7. Limestone is mostly calcium carbonate, CaCO3, but also contains other minerals. When heated, the CaCO3
decomposes into CaO and CO2. A 1.605 g sample of limestone was heated and gave off 0.657 g of CO2.
(a) Formulate the equation for the thermal decomposition of calcium carbonate.
(b) Determine the percentage mass of CaCO3 in the limestone.
(c) State the assumptions that you are making in this calculation.
8. Methanol, CH3OH, is a useful fuel that can be made as follows: CO(g) + 2H2(g) → CH3OH(l) A reaction
mixture used 12.0 g of H2 and 74.5 g of CO.
(a) Determine the theoretical yield of CH3OH.
(b) Calculate the amount of the excess reactant that remains unchanged at the end of the reaction.
9. The dry-cleaning solvent 1,2-dichloroethane, C2H4Cl2, is prepared from the following reaction:
C2H4(g) + Cl2(g) → C2H4Cl2(l)
Determine the mass of product that can be formed from 15.40 g of C2H4 and 3.74 g of Cl2.
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10. Calcium carbonate, CaCO3, is able to remove sulfur dioxide, SO2, from waste gases by a reaction in which
they react in a 1 : 1 stoichiometric ratio to form equimolar amounts of CaSO3. When 255 g of CaCO3
reacted with 135 g of SO2, 198 g of CaSO3 were formed. Determine the percentage yield of CaSO3.
11. Pentyl ethanoate, CH3COOC5H11, which smells like bananas, is produced from the esterification reaction:
CH3COOH(aq) + C5H11OH(aq) → CH3COOC5H11(aq) + H2O(l) A reaction uses 3.58 g of CH3COOH and
4.75 g of C5H11OH and has a yield of 45.00%. Determine the mass of ester that forms.
12. A chemist has to make a 100 g sample of chlorobenzene, C6H5Cl, from the following reaction:
C6H6 + Cl2 → C6H5Cl + HCl Determine the minimum quantity of benzene, C6H6, that can be used to achieve
this with a yield of 65%.
