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Chemistry 1010 Sections 1, 2, 3 and 10 Loader (Fall 2004)
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Chemistry 1010
Handout 3: Moles and Stoichiometry - 2
1.
Calculate the empirical formula for the compounds with
analysis:
(a)
(b)
(c)
(d)
46.3% Li; 53.7% O
68.4% Cr; 31.6% O
22.6% K; 35.4% Cr; 38.0% O
39.7% K; 27.9% Mn; 32.5% O
2.
Aluminum metal reacts with oxygen gas as follows:
4 Al(s) + 3 O2(g) → 2 Al2O3(s)
What mass of Al2O3(s) is produced when 3.5020 g of
aluminum is burned in air and what mass of oxygen gas is
used?
3.
Calculate the maximum mass of copper(II) oxide that could
be produced when 6.25 g of copper(II) carbonate is heated:
CuCO3(s) → CuO(s) + CO2(g)
4.
What mass of CS2 is produced when 17.5 g of C are
allowed to react with 39.5 g of SO2 according to the
equation:
5 C(s) + 2 SO2(g) → CS2(l) + 4 CO(g)?
5.
When 2.16 g of osmium, Os, was converted to the oxide,
2.89 g of the oxide was obtained. What was the empirical
formula of the osmium oxide that formed?
6.
When 0.15 mol of potassium superoxide, KO2, and 0.10 mol
H2O are mixed the following reaction takes place:
KO2 + H2O → KOH + O2
(a) Balance the equation.
(b) What is the limiting reagent?
(c) What is the theoretical yield of oxygen (in grams)?
7.
8.
Methyl salicylate (oil of wintergreen), C8H8O3, is prepared by
the reaction of salicylic acid, C7H6O3, with methanol, CH4O.
C7H6O3 + CH4O → C8H8O3
When 1.50 g of salicylic acid, C7H6O3, reacts with 11.20 g of
methanol, CH4O, the reaction gave 1.24 g of methyl
salicylate, C8H8O3.
(a) Calculate the theoretical yield (in grams) of methyl
salicylate.
(b) Calculate the percentage yield of methyl salicylate.
Hydrogen gas can be made to react with nitrogen gas to
give ammonia gas:
____ H2(g) + ____ N2(g) → ____ NH3(g)
(a) Balance the above equation.
(b) How many mole of ammonia can be made from 32.44 g
of hydrogen gas?
(c) If 20.0 g of hydrogen is allowed to react with 20.0 g of
nitrogen, what is the theoretical (maximum possible)
yield of ammonia (in grams)?
(d) If only 19.7 g of ammonia is obtained from the reaction,
what is the percentage yield?
9.
The reaction: SiO2(s) + 4 HF(g) → SiF4(g) + 2 H2O(g)
produced 2.55 g of H2O when 12.2 g of SiO2 was treated
with a small excess of HF. (Note: Not all of the SiO2 reacts)
(a) What mass of SiF4 was formed?
(b) What was the percentage yield of the SiF4?
(c) What mass of SiO2 was left unreacted?
10. When calcium carbonate, is heated strongly it decomposes:
CaCO3(s) → CaO(s) + CO2(g)
(a) If 49.98 g of CaCO3 is completely decomposed what
mass of CaO(s) is produced?
(b) What mass of CaCO3 is needed to make 50.0 g of
carbon dioxide, CO2(g)?
(c) A 250.0 g sample of CaCO3(s) was heated for 30
minutes and the residue was then cooled. The mass of
the cold residue was 178.8 g.
(i) Was the reaction complete? Explain.
(ii) If the reaction was incomplete, how much of each
of CaCO3 and CaO was present in the residue?
11. When 0.5000 g of aluminum, Al, reacted with chlorine gas,
Cl2(g), a chloride of aluminum was formed as pale yellow
solid that weighed 2.4710 g.
(a) What mass of chlorine has combined with the
aluminum?
(b) What is the empirical formula for the compound?
12. Chromium metal can be produced in an electric furnace by
the reaction:
2 Cr2O3(s) + 3 Si(s) + 3 CaO(s) → 4 Cr(s) + 3 CaSiO3(s)
(a) How many mole of Cr2O3(s) are needed to make 5 mole
of Cr(s).
(b) How many mole of silicon, Si(s), are used in making 1
mole of chromium, Cr(s)?
(c) How many tonne (metric tonne = 1000 kg) of chromium
can be made from 5.00 tonne of Cr2O3(s)?
13. The concentration of the solution described:
(a) 100.00 mL of a solution containing 0.1500 mol of
NaNO3 (sodium nitrate).
(b) 250.0 mL of a solution containing 5.5087 g of CaCl2
(calcium chloride).
(c) The concentration of the NaOH solution formed when
1.321 g of sodium reacted with water and the volume of
the final solution was 76.64 mL.
(d) 0.3010 g of CuSO4.5H2O(s) is dissolved and made up
to 200.00 mL with water.
(e) The solution formed when 10.00 mL of a 0.500 mol.L-1
hydrochloric acid, HCl(aq), is diluted to 250.0 mL?
14. Calculate the number of moles and the mass of each
substance in the solutions.
(a) 20.00 mL of 0.150 mol.L-1 KNO3(aq)
(b) 150 mL of 1.331 x 10-2 mol.L-1 magnesium chloride
solution.