1 Ch 4 Practice -- Stoichiometry
AP Chemistry 2011-12
1984 Multiple Choice Questions59. When 70. milliliter of 3.0-molar Na2CO3 is added to 30. milliliters of 1.0-molar NaHCO3 the resulting concentration of Na+ is
(A) 2.0 M (B) 2.4 M (C) 4.0 M
(D) 4.5 M (E) 7.0 M
68. A 20.0-milliliter sample of 0.200-molar K2CO3 solution is added to 30.0 milliliters of 0.400-molar Ba(NO3)2 solution. Barium carbonate precipitates. The concentration of barium ion, Ba2+, in solution after reaction is
(A) 0.150 M (B) 0.160 M (C) 0.200 M
(D) 0.240 M (E) 0.267 M
79. 5 Fe2+ + MnO4−
+ 8 H+ ' 5 Fe3+ + Mn2+ + 4H2O
In a titration experiment based on the equation above, 25.0 milliliters of an acidified Fe2+ solution requires 14.0 milliliters of standard 0.050-molar MnO4
- solution to reach the equivalence point. The concentration of Fe2+ in the original solution is
(A) 0.0010 M (B) 0.0056 M (C) 0.028 M
(D) 0.090 M (E) 0.14 M
1994
16. Commercial vinegar was titrated with NaOH solution to determine the content of acetic acid, HC2H3O2. For 20.0 milliliters of the vinegar, 32.0 milliliters of 0.500-molar NaOH solution was required. What was the concentration of acetic acid in the vinegar if no other acid was present?
(A) 1.60 M (B) 0.800 M (C) 0.640 M
(D) 0.600 M (E) 0.400 M
53. If 87 grams of K2SO4 (molar mass 174 grams) is dissolved in enough water to make 250 milliliters of solution, what are the concentrations of the potassium and the sulfate ions?
[K+] [SO4 2-] (A) 0.020 M 0.020 M (B) 1.0 M 2.0 M (C) 2.0 M 1.0 M (D) 2.0 M 2.0 M (E) 4.0 M 2.0 M
55. What volume of 0.150-molar HCl is required to neutralize 25.0 milliliters of 0.120-molar Ba(OH)2? (A) 20.0 mL
(B) 30 0 mL (C) 40.0 mL
(D) 60.0 mL (E) 80.0 mL
2
56. It is suggested that SO2 (molar mass 64 grams), which contributes to acid rain, could be removed from a stream of waste gases by bubbling the gases through 0.25-molar KOH, thereby producing K2SO3. What is the maximum mass of SO2 that could be removed by 1,000. liters of the KOH solution?(A) 4.0 kg (B) 8.0 kg (C) 16 kg
(D) 20. kg (E) 40. kg
1999
20. What mass of Au is produced when 0.0500 mol of Au2S3 is reduced completely with excess H2? (A) 9.85 g
(B) 19.7 g (C) 24.5 g
(D) 39.4 g (E) 48.9 g
33. A 1.0 L sample of an aqueous solution contains 0.10 mol of NaCl and 0.10 mol of CaCl2. What is the minimum number of moles of AgNO3 that must be added to the solution in order to precipitate all of the Cl- as AgCl(s)? (Assume that AgCl is insoluble.)
(A) 0.10 mol (B) 0.20 mol (C) 0.30 mol
(D) 0.40 mol (E) 0.60 mol
10 HI + 2 KMnO4 + 3 H2SO4 → 5 I2 + 2 MnSO4 + K2SO4 + 8 H2O
55. According to the balanced equation above, how many moles of HI would be necessary to produce 2.5 mol of I2, starting with 4.0 mol of KMnO4 and 3.0 mol of H2SO4 ?
(A) 20.
(B) 10.
(C) 8.0
(D) 5.0 (E) 2.5
2002
24. A compound contains 1.10 mol of K, 0.55 mol of Te, and 1.65 mol of O. What is the simplest formula of this compound?
(A) KTeO (B) KTe2O (C) K2TeO3 (D) K2TeO6 (E) K4TeO6
26. Approximately what mass of CuSO4 ⋅ 5H2O (250 g mol-l) is required to prepare 250 mL of 0.10 M copper(II) sulfate solution?
(A) 4.0 g (B) 6.2 g (C) 34 g (D) 85 g (E) 140 g
2N2H4(g) + N2O4(g) → 3 N2(g) + 4H2O(g)
58. When 8.0 g of N2H4 (32 g mol-1) and 92 g of N2O4 (92 g mol-l) are mixed together and react according to the equation above, what is the maximum mass of H2O that can be produced?
(A) 9.0 g (B) 18 g (C) 36 g (D) 72 g (E) 144 g
3
2H2O(l
) + 4MnO4−(aq) + 3ClO2−(aq) → 4MnO2(s) + 3ClO4−(aq) + 4OH−(aq) 60. According to the balanced equation above, how many moles of ClO2−
(aq) are needed to react completely with 20. mL of 0.20 M KMnO4 solution?
(A) 0.0030 mol (B) 0.0053 mol (C) 0.0075 mol (D) 0.013 mol (E) 0.030 mol
69. If 200. mL of 0.60 M MgCl2(aq) is added to 400. mL of distilled water, what is the concentration of Mg2+(aq) in the resulting solution? (Assume volumes are additive.)
(A) 0.20 M (B) 0.30 M (C) 0.40 M (D) 0.60 M (E) 1.2 M
AP Free Response -- Stoichiometry 1995 B
A sample of dolomitic limestone containing only CaCO3 and MgCO3 was analyzed.
(a) When a 0.2800 gram sample of this limestone was decomposed by heating, 75.0 milliliters of CO2 at 750 mm Hg and 20°C were evolved. How many grams of CO2 were produced?
(b) Write equations for the decomposition of both carbonates described above.
(c) It was also determined that the initial sample contained 0.0448 gram of calcium. What percent of the limestone by mass was CaCO3?
(d) How many grams of the magnesium-containing product were present in the sample in (a) after it had been heated?
4
2000 B(c) A 0.345 g sample of anhydrous BeC2O4 which contains an inert impurity, was dissolved in sufficient water to produce 100. mL of solution. A 20.0 mL portion of the solution was titrated with KMnO4(aq). The balanced equation for the reaction that occurred is as follows.
16 H+(aq) + 2 MnO4−(aq) + 5 C2O42−(aq) → 2 Mn2+(aq) + 10 CO2(g) + 8 H2O(
l
).The volume of 0.0150 M KMnO4(aq) required to reach the equivalence point was 17.80 mL.
(i) Identify the reducing agent in the titration reaction.
(ii) For the titration at the equivalence point, calculate the number of moles of each of the following that reacted.
• MnO4−(aq)
• C2O42−
(aq)
(iii) Calculate the total number of moles of C2O42−
(aq)that were present in the 100. mL of prepared solution.
(iv) Calculate the mass percent of BeC2O4(s) in the impure 0.345 g sample.
2001 B
Answer the following questions about acetylsalicylic acid, the active ingredient in aspirin.
(a) The amount of acetylsalicylic acid in a single aspirin tablet is 325 mg, yet the tablet has a mass of 2.00 g.
Calculate the mass percent of acetylsalicylic acid in the tablet.
(b) The elements contained in acetylsalicylic acid are hydrogen, carbon, and oxygen. The combustion of 3.000 g of the pure compound yields 1.200 g of water and 3.72 L of dry carbon dioxide, measured at 750. mm Hg and 25°C. Calculate the mass, in g, of each element in the 3.000 g sample.
