ACS Exam (Chem 161 ) verified question
with 100% answers
1. A 10.0 mL portion of 0.010 M HCl is added to 100.0 mL of water. What is the pH
of the resulting solution?
a. between 3.02 and 3.10
b. between 2.90 and 3.01
c. between 2.02 and 2.10
d. between 1.90 and 2.01
- ANSWER-a) between 3.02 and 3.10
2. A 1400 g sample of stream water contains 12.2 ppm of mercury. What is the
mass of Hg in the sample?
a. 0.11 mg
b. 2.4 mg
c. 8.7 mg
d. 17 mg
- ANSWER-d) 17 mg
3. A 2.50 g sample of naphthalene, C10H8, was dissolved in 100 g of benzene.
What is the freezing point of the benzene solution? The freezing point of pure
benzene is 5.45 C; Kf = 5.07 C/m
a. -0.989 C
b. 0.989 C
c. 4.46 C
d. 6.44 C
- ANSWER-c) 4.46 C
4. A 235/92 U atom undergoes nuclear fission by being bombarded with a neutron
to produce a total of four neutrons, a 140/55 Cs atom, and
- ANSWER-92/37 Rb
5. A 250-mL bottle of a sports drink solution contains 4.50% by mass of sodium
chloride. What is the molal concentration of sodium chloride in this bottle of
sports drink?
a. 0.806 m
b. 0.770 m
, c. 0.180 m
d. 0.0113 m
- ANSWER-a) 0.806 m
6. A catalyst increases the rate of a reaction by
a. changing the mechanism of the reaction
b. increasing the activation energy of the reaction
c. increasing the concentration of one or more reactants
d. decreasing the difference in relative energy of the reactants and products
- ANSWER-a) changing the mechanism of the reaction
7. A catalyst is added to a system at equilibrium. Which statement is true?
a. the temperature will decrease
b. the equilibrium constant will increase
c. the concentration of products will decrease
d. if the system is disturbed, it will return to equilibrium faster
- ANSWER-d) if the system is disturbed, it will return to equilibrium faster
8. A certain reaction has delta H = -75 kJ/mol and an activation energy of 40 kJ/mol.
A catalyzed is found that lowers the activation energy of the forward reaction by
15 kJ/mol. What is the activation energy of the reverse in the presence of the
same catalyst?
a. 25 kJ/mol
b. 60 kJ/mol
c. 90 kJ/mol
d. 100 kJ/mol
- ANSWER-d) 100 kJ/mol
9. A mixture of 100 g of K2Cr2)7 and 200 g of water is stirred at 60C until no more
of the salt dissolves. The resulting solution is poured off into a separate beaker,
leaving the undissolved solid behind. The solution is now cooled to 20C. What
mass of K2Cr2O7 crystallizes from the solution during the cooling?
a. 9g
b. 18 g
c. 31 g
d. 62 g
- ANSWER-b) 62 g
10. A mixture of 2.0 mol of CO(g) and 2.0 mol of H2O(g) was allowed to come to
equilibrium in a 10.0-L flask at a high temperature. If Kc = 4.0, what is the molar
concentration of H2(g) in the equilibrium mixture? CO(g) + H2O(g) = CO(g) +
H2(g)
, a. 0.67 M
b. 0.40 M
c. 0.20 M
d. 0.13 M
- ANSWER-d) 0.13 M
11. A sample of "hard" water contains about 2.0 x 10^-2 mol of Ca^2+ ions per liter.
What is the maximum concentration of fluoride ion that could be present in hard
water? Assume fluoride is the only anion present that will precipitate calcium ion
(Ksp of CaF2(s) at 25C = 4.0 x 10^-11)
- ANSWER-4.4 x 10^-5 M
12. A saturated solution of Al(OH)3 has a molar solubility of 2.9 x 10^-9 M at a
certain temperature. What is the Ksp of MgF2 at this temperature?
- ANSWER-b) 1.9 x 10^-23
13. A saturated solution of MgF2 contains 1.6 x 10^-3 mol of MgF2 per liter at a
certain temperature. What is the Ksp of MgF2 at this temperature?
- ANSWER-b) 1.6 x 10^-8
14. A solution contains 0.002 M Be2+ and 0.002 M Ca2+. What happens when
NaOH(s) is added to bring the hydroxide ion concentration to 0.10 M?
- ANSWER-both Be(OH)2 and Ca(OH)2 precipitate
15. A solution contains 0.002 M Pb2+ and 0.002 M Ag+. What happens when
NaCl(s) is added to bring the chloride ion concentration to 0.01 M?
a. neither PbCl2 nor AgCl will precipitate
b. Both PbCl2 and AgCl precipitate
c. Only PbCl2 precipitates
d. only AgCl precipitates
- ANSWER-d) only AgCl precipitates
16. A solution of NaCl in water has a concentration of 20.5% by mass. What is the
molal concentration of the solution?
a. 0.205 m
b. 0.258 m
c. 3.51 m
d. 4.41 m
- ANSWER-percent by mass = (mass by one component)/(total mass) x
100% = (mass solute)/((mass solution) x 100% = (mass solute)/(mass
solute + mass solvent) x 100%
17. molal concentration = (mol solute)/(mass solvent kg)
, 18. SOLUTION: 100 g solution - 20.5 g NaCl = 79.5 g water
i. (20.5 g NaCl)(mol NaCl/58.44 g NaCl)/0.0795 kg water = 4.41 m
19. A solution was made by adding 800 g of ethanol, C2H5OH, to 8.0 x 10^3 g of
water. How much would this lower the freezing point
a. 3.2 C
b. 4.1 C
c. 8.2 C
d. 16 C
- ANSWER-b) 4.1 C
20. a spontaneous reaction has a negative delta S. what must be true about the
reaction?
- ANSWER-the reaction is exothermic and the temperature is sufficiently low
21. A student mixes 20.0 g of a salt in 100.0 g of water at 20C and obtains a
homogeneous solution. Which salt could this be and why?
a. KCl because it is saturated
b. KCl because it is unsaturated
c. KNO3 because it is saturated
d. KNO3 because it is unsaturated
- ANSWER-d) KNO3 because it is unsaturated
22. A technician has the measured osmotic pressure of a solution to determine the
molar mass of a covalent solute. Which other information would need to be
measured in order to determine the molar mass?
1. Temperature
2. Volume of solution
3. Mass of solute
23. only I
24. only III
25. only I and II
26. I, II, and III
- ANSWER-d) I, II, and III
27. According to the Nernst Equation, when Ecell = 0 then
- ANSWER-Q = K
28. Activation energy an be experimentally determined from the slope of the plot of
a. k vs. 1/T
b. k vs. lnT
with 100% answers
1. A 10.0 mL portion of 0.010 M HCl is added to 100.0 mL of water. What is the pH
of the resulting solution?
a. between 3.02 and 3.10
b. between 2.90 and 3.01
c. between 2.02 and 2.10
d. between 1.90 and 2.01
- ANSWER-a) between 3.02 and 3.10
2. A 1400 g sample of stream water contains 12.2 ppm of mercury. What is the
mass of Hg in the sample?
a. 0.11 mg
b. 2.4 mg
c. 8.7 mg
d. 17 mg
- ANSWER-d) 17 mg
3. A 2.50 g sample of naphthalene, C10H8, was dissolved in 100 g of benzene.
What is the freezing point of the benzene solution? The freezing point of pure
benzene is 5.45 C; Kf = 5.07 C/m
a. -0.989 C
b. 0.989 C
c. 4.46 C
d. 6.44 C
- ANSWER-c) 4.46 C
4. A 235/92 U atom undergoes nuclear fission by being bombarded with a neutron
to produce a total of four neutrons, a 140/55 Cs atom, and
- ANSWER-92/37 Rb
5. A 250-mL bottle of a sports drink solution contains 4.50% by mass of sodium
chloride. What is the molal concentration of sodium chloride in this bottle of
sports drink?
a. 0.806 m
b. 0.770 m
, c. 0.180 m
d. 0.0113 m
- ANSWER-a) 0.806 m
6. A catalyst increases the rate of a reaction by
a. changing the mechanism of the reaction
b. increasing the activation energy of the reaction
c. increasing the concentration of one or more reactants
d. decreasing the difference in relative energy of the reactants and products
- ANSWER-a) changing the mechanism of the reaction
7. A catalyst is added to a system at equilibrium. Which statement is true?
a. the temperature will decrease
b. the equilibrium constant will increase
c. the concentration of products will decrease
d. if the system is disturbed, it will return to equilibrium faster
- ANSWER-d) if the system is disturbed, it will return to equilibrium faster
8. A certain reaction has delta H = -75 kJ/mol and an activation energy of 40 kJ/mol.
A catalyzed is found that lowers the activation energy of the forward reaction by
15 kJ/mol. What is the activation energy of the reverse in the presence of the
same catalyst?
a. 25 kJ/mol
b. 60 kJ/mol
c. 90 kJ/mol
d. 100 kJ/mol
- ANSWER-d) 100 kJ/mol
9. A mixture of 100 g of K2Cr2)7 and 200 g of water is stirred at 60C until no more
of the salt dissolves. The resulting solution is poured off into a separate beaker,
leaving the undissolved solid behind. The solution is now cooled to 20C. What
mass of K2Cr2O7 crystallizes from the solution during the cooling?
a. 9g
b. 18 g
c. 31 g
d. 62 g
- ANSWER-b) 62 g
10. A mixture of 2.0 mol of CO(g) and 2.0 mol of H2O(g) was allowed to come to
equilibrium in a 10.0-L flask at a high temperature. If Kc = 4.0, what is the molar
concentration of H2(g) in the equilibrium mixture? CO(g) + H2O(g) = CO(g) +
H2(g)
, a. 0.67 M
b. 0.40 M
c. 0.20 M
d. 0.13 M
- ANSWER-d) 0.13 M
11. A sample of "hard" water contains about 2.0 x 10^-2 mol of Ca^2+ ions per liter.
What is the maximum concentration of fluoride ion that could be present in hard
water? Assume fluoride is the only anion present that will precipitate calcium ion
(Ksp of CaF2(s) at 25C = 4.0 x 10^-11)
- ANSWER-4.4 x 10^-5 M
12. A saturated solution of Al(OH)3 has a molar solubility of 2.9 x 10^-9 M at a
certain temperature. What is the Ksp of MgF2 at this temperature?
- ANSWER-b) 1.9 x 10^-23
13. A saturated solution of MgF2 contains 1.6 x 10^-3 mol of MgF2 per liter at a
certain temperature. What is the Ksp of MgF2 at this temperature?
- ANSWER-b) 1.6 x 10^-8
14. A solution contains 0.002 M Be2+ and 0.002 M Ca2+. What happens when
NaOH(s) is added to bring the hydroxide ion concentration to 0.10 M?
- ANSWER-both Be(OH)2 and Ca(OH)2 precipitate
15. A solution contains 0.002 M Pb2+ and 0.002 M Ag+. What happens when
NaCl(s) is added to bring the chloride ion concentration to 0.01 M?
a. neither PbCl2 nor AgCl will precipitate
b. Both PbCl2 and AgCl precipitate
c. Only PbCl2 precipitates
d. only AgCl precipitates
- ANSWER-d) only AgCl precipitates
16. A solution of NaCl in water has a concentration of 20.5% by mass. What is the
molal concentration of the solution?
a. 0.205 m
b. 0.258 m
c. 3.51 m
d. 4.41 m
- ANSWER-percent by mass = (mass by one component)/(total mass) x
100% = (mass solute)/((mass solution) x 100% = (mass solute)/(mass
solute + mass solvent) x 100%
17. molal concentration = (mol solute)/(mass solvent kg)
, 18. SOLUTION: 100 g solution - 20.5 g NaCl = 79.5 g water
i. (20.5 g NaCl)(mol NaCl/58.44 g NaCl)/0.0795 kg water = 4.41 m
19. A solution was made by adding 800 g of ethanol, C2H5OH, to 8.0 x 10^3 g of
water. How much would this lower the freezing point
a. 3.2 C
b. 4.1 C
c. 8.2 C
d. 16 C
- ANSWER-b) 4.1 C
20. a spontaneous reaction has a negative delta S. what must be true about the
reaction?
- ANSWER-the reaction is exothermic and the temperature is sufficiently low
21. A student mixes 20.0 g of a salt in 100.0 g of water at 20C and obtains a
homogeneous solution. Which salt could this be and why?
a. KCl because it is saturated
b. KCl because it is unsaturated
c. KNO3 because it is saturated
d. KNO3 because it is unsaturated
- ANSWER-d) KNO3 because it is unsaturated
22. A technician has the measured osmotic pressure of a solution to determine the
molar mass of a covalent solute. Which other information would need to be
measured in order to determine the molar mass?
1. Temperature
2. Volume of solution
3. Mass of solute
23. only I
24. only III
25. only I and II
26. I, II, and III
- ANSWER-d) I, II, and III
27. According to the Nernst Equation, when Ecell = 0 then
- ANSWER-Q = K
28. Activation energy an be experimentally determined from the slope of the plot of
a. k vs. 1/T
b. k vs. lnT
