CHEM 101L QUESTIONS AND ANSWERS
A. 0.01998 mol
If the balanced equation for the reaction of calcium carbonate with hydrochloric acid is:
2 HCl (aq) + CaCO3 (s) —► CaCl2 (aq) + CO2 (g) + H2O (l)
How many moles of HCl can be neutralized by an antacid containing 1000 mg
(1.000x103 mg) of calcium carbonate? (CaCO3 MW = 100.1 g/mol)
A. 0.01998 mol
B. 9.99 x 10E-3 mol
C. 0.009990 mol
D. 200.2 mol
E. 2.00 x 10E-2 mol
F. 100.1 mol
B. The powdered tablet is immersed in the solution.
During the second trial of the neutralization of the crushed antacid tablet by an excess
of HCl, a student notices that the pH of the solution has not increased. The first trial ran
as expected. The student should check the following probable issues to be sure the
experiment is set up correctly:
A. The tablet contains too much base.
B. The powdered tablet is immersed in the solution.
C. The tablet contains too little base.
D. The pH probe is correctly calibrated.
B. 750 mg calcium carbonate
D. There are more moles of base
The tablet containing _______________(answer a or b), should neutralize more acid
because __________________(answers c-h). Select all correct answers.
CaCO3 MW = 100.1 g/mol
Mg(OH)2 MW = 58.32 g/mol
CaCO3 + 2 HCl —► CaCl2 + H2O + CO2
Mg(OH)2 + 2 HCl —► MgCl2 + 2 H2O
A. 500 mg calcium carbonate + 135 mg magnesium hydroxide
B. 750 mg calcium carbonate
C. There are more mg of active ingredient.
D. There are more moles of base.
E. Each magnesium hydroxide reacts with more moles of acid.
F. Each calcium carbonate reacts with more moles of acid.
, G. The molar mass of Mg(OH)2 is smaller, giving more moles of based for the same
mass.
H. The molar mass of CaCO3 is larger, giving more moles of base for the same mass.
B. Causes a loud popping noise.
E. Grows warm
Based on your observations in Experiment 5, an exothermic reaction may be identified
via observation in the lab when it: (select all correct answers)
A. Dissolves a solid reactant.
B. Causes a loud popping noise.
C. Produces bubbles.
D. Forms a precipitate.
E. Grows warm.
B. None of these is endothermic.
Which of the three reactions used in Experiment 5 are endothermic: (select all correct
answers)
A. 2H2 (g) + O2 (g) —► 2 H2O (g)
B. None of these is endothermic.
C. 2HCl(aq) + Zn(s) —► H2(g) + ZnCl2(aq)
D. 2H2O2(aq) + (catalase) —► 2 H2O(l) + O2(g)
D. Collecting water vapor in the pipette bulb
E. The presence of liquid water in the pipette bulb
F. Losing H2 gas because it is less dense than air
Potential source(s) of error in Experiment 5 include: (select all correct answers)
A. Losing O2 gas because it is more dense than air.
B. Using an excess of yeast in the reaction with H2O2
C. Using an excess of HCl in the reaction with zinc
D. Collecting water vapor in the pipette bulb
E. The presence of liquid water in the pipette bulb
F. Losing H2 gas because it is less dense than air
G. Mixing the two reagent gases in the pipette bulb
B. 9.36 kJ
In a calorimetry experiment, 50.0 mL each of two dilute aqueous solutions are combined
and produce an extrapolated T = -22.4˚C. If the density of each solution is assumed to
be equal to that of water (at 20˚C, d = 0.9982 g/mL), and the specific heat of the
solution is also equal to that of water (4.186 J/g˚C), the value of qrxn would be:
A. -17.7 kJ
B. 9.36 kJ
C. 17.7 kJ
D. -9.36 kJ
E. -9.38 kJ
F. 9.38 kJ
A. 0.01998 mol
If the balanced equation for the reaction of calcium carbonate with hydrochloric acid is:
2 HCl (aq) + CaCO3 (s) —► CaCl2 (aq) + CO2 (g) + H2O (l)
How many moles of HCl can be neutralized by an antacid containing 1000 mg
(1.000x103 mg) of calcium carbonate? (CaCO3 MW = 100.1 g/mol)
A. 0.01998 mol
B. 9.99 x 10E-3 mol
C. 0.009990 mol
D. 200.2 mol
E. 2.00 x 10E-2 mol
F. 100.1 mol
B. The powdered tablet is immersed in the solution.
During the second trial of the neutralization of the crushed antacid tablet by an excess
of HCl, a student notices that the pH of the solution has not increased. The first trial ran
as expected. The student should check the following probable issues to be sure the
experiment is set up correctly:
A. The tablet contains too much base.
B. The powdered tablet is immersed in the solution.
C. The tablet contains too little base.
D. The pH probe is correctly calibrated.
B. 750 mg calcium carbonate
D. There are more moles of base
The tablet containing _______________(answer a or b), should neutralize more acid
because __________________(answers c-h). Select all correct answers.
CaCO3 MW = 100.1 g/mol
Mg(OH)2 MW = 58.32 g/mol
CaCO3 + 2 HCl —► CaCl2 + H2O + CO2
Mg(OH)2 + 2 HCl —► MgCl2 + 2 H2O
A. 500 mg calcium carbonate + 135 mg magnesium hydroxide
B. 750 mg calcium carbonate
C. There are more mg of active ingredient.
D. There are more moles of base.
E. Each magnesium hydroxide reacts with more moles of acid.
F. Each calcium carbonate reacts with more moles of acid.
, G. The molar mass of Mg(OH)2 is smaller, giving more moles of based for the same
mass.
H. The molar mass of CaCO3 is larger, giving more moles of base for the same mass.
B. Causes a loud popping noise.
E. Grows warm
Based on your observations in Experiment 5, an exothermic reaction may be identified
via observation in the lab when it: (select all correct answers)
A. Dissolves a solid reactant.
B. Causes a loud popping noise.
C. Produces bubbles.
D. Forms a precipitate.
E. Grows warm.
B. None of these is endothermic.
Which of the three reactions used in Experiment 5 are endothermic: (select all correct
answers)
A. 2H2 (g) + O2 (g) —► 2 H2O (g)
B. None of these is endothermic.
C. 2HCl(aq) + Zn(s) —► H2(g) + ZnCl2(aq)
D. 2H2O2(aq) + (catalase) —► 2 H2O(l) + O2(g)
D. Collecting water vapor in the pipette bulb
E. The presence of liquid water in the pipette bulb
F. Losing H2 gas because it is less dense than air
Potential source(s) of error in Experiment 5 include: (select all correct answers)
A. Losing O2 gas because it is more dense than air.
B. Using an excess of yeast in the reaction with H2O2
C. Using an excess of HCl in the reaction with zinc
D. Collecting water vapor in the pipette bulb
E. The presence of liquid water in the pipette bulb
F. Losing H2 gas because it is less dense than air
G. Mixing the two reagent gases in the pipette bulb
B. 9.36 kJ
In a calorimetry experiment, 50.0 mL each of two dilute aqueous solutions are combined
and produce an extrapolated T = -22.4˚C. If the density of each solution is assumed to
be equal to that of water (at 20˚C, d = 0.9982 g/mL), and the specific heat of the
solution is also equal to that of water (4.186 J/g˚C), the value of qrxn would be:
A. -17.7 kJ
B. 9.36 kJ
C. 17.7 kJ
D. -9.36 kJ
E. -9.38 kJ
F. 9.38 kJ
