Form Code A: CHM 2046 Practice Exam 1 (Ch. 16, 17, 18) Name_______________
Instructions: On your Scantron form, enter and bubble your name, UFID, and Form Code (see above).
Turn in only your Scantron. You may keep your exam sheet and any other papers. Check bubbling
carefully: bubbling errors are non-negotiable. As on all graded events, the Honor Code applies.
Correct answers on the last page.
1. Consider the hypothetical reaction and rate data below. Determine the form of the rate-law
expression (i.e., determine the values of a and b in rate = k[A]a[B]b) and also the value of the specific
rate constant, k. Which of the answers below would be the initial rate of reaction for [A]initial = 0.40
M and [B]initial = 0.10 M? 3A + 2B → Products
Run [A]initial [B]initial Initial Rate of Reaction
(moles per liter per second)
1 0.10 M 0.10 M 4.0 x 10–4
2 0.20 M 0.30 M 4.8 x 10–3
3 0.30 M 0.10 M 3.6 x 10–3
(1) 1.6 x 10–4 M•s–1 (2) 3.4 x 10–3 M•s–1 (3) 1.2 x 10–3 M•s–1
(4) 4.8 x 10–4 M•s–1 (5) 6.4 x 10–3 M•s–1
2. Cyclopropane is converted to propene in a first-order process. The rate constant is 5.4 × 10 –2 hr–1. If the
initial concentration of cyclopropane is 0.150 M, what will its concentration be after 22.0 hours?
(1) 0.0457 M (2) 0.105 M (3) 0.127 M (4) 0.492 M (5) none of the above
3. Sodium-24 is a radioactive isotope that decays via first order kinetics and has a half-life of 15 hours.
What fraction of an original sample of sodium-24 will decompose in 3 days?
(1) 4% (2) 13% (3) 50% (4) 87% (5) 96%
4. In going from room temperature (25.0 °C) to 10 °C above room temperature, the rate of a reaction
doubles. Calculate the activation energy for the reaction.
(1) 157.2 kJ/mol (2) 103.8 kJ/mol (3) 52.9 kJ/mol (4) 6.4 kJ/mol (5) < 1 kJ/mol
5. Consider the reaction
2NH3(g) → N2(g) + 3H2(g)
If the rate ∆[H2]/∆t is 0.030 mol L–1 s–1, then ∆[NH3]/∆t is
(1) -0.045 M/s (2) -0.030 M/s (3) -0.020 M/s (4) -0.010 M/s (5) none of the above
6. At 25°C, 0.138 mg AgBr dissolves in 10.0 L of water. What is the equilibrium constant for the reaction
below? AgBr(s) Ag+(aq) + Br–(aq)
(1) 5.40 x 10–15 (2) 5.40 x 10–13 (3) 1.90 x 10–8 (4) 7.35 x 10–7 (5) 1.90 x 10–6
Instructions: On your Scantron form, enter and bubble your name, UFID, and Form Code (see above).
Turn in only your Scantron. You may keep your exam sheet and any other papers. Check bubbling
carefully: bubbling errors are non-negotiable. As on all graded events, the Honor Code applies.
Correct answers on the last page.
1. Consider the hypothetical reaction and rate data below. Determine the form of the rate-law
expression (i.e., determine the values of a and b in rate = k[A]a[B]b) and also the value of the specific
rate constant, k. Which of the answers below would be the initial rate of reaction for [A]initial = 0.40
M and [B]initial = 0.10 M? 3A + 2B → Products
Run [A]initial [B]initial Initial Rate of Reaction
(moles per liter per second)
1 0.10 M 0.10 M 4.0 x 10–4
2 0.20 M 0.30 M 4.8 x 10–3
3 0.30 M 0.10 M 3.6 x 10–3
(1) 1.6 x 10–4 M•s–1 (2) 3.4 x 10–3 M•s–1 (3) 1.2 x 10–3 M•s–1
(4) 4.8 x 10–4 M•s–1 (5) 6.4 x 10–3 M•s–1
2. Cyclopropane is converted to propene in a first-order process. The rate constant is 5.4 × 10 –2 hr–1. If the
initial concentration of cyclopropane is 0.150 M, what will its concentration be after 22.0 hours?
(1) 0.0457 M (2) 0.105 M (3) 0.127 M (4) 0.492 M (5) none of the above
3. Sodium-24 is a radioactive isotope that decays via first order kinetics and has a half-life of 15 hours.
What fraction of an original sample of sodium-24 will decompose in 3 days?
(1) 4% (2) 13% (3) 50% (4) 87% (5) 96%
4. In going from room temperature (25.0 °C) to 10 °C above room temperature, the rate of a reaction
doubles. Calculate the activation energy for the reaction.
(1) 157.2 kJ/mol (2) 103.8 kJ/mol (3) 52.9 kJ/mol (4) 6.4 kJ/mol (5) < 1 kJ/mol
5. Consider the reaction
2NH3(g) → N2(g) + 3H2(g)
If the rate ∆[H2]/∆t is 0.030 mol L–1 s–1, then ∆[NH3]/∆t is
(1) -0.045 M/s (2) -0.030 M/s (3) -0.020 M/s (4) -0.010 M/s (5) none of the above
6. At 25°C, 0.138 mg AgBr dissolves in 10.0 L of water. What is the equilibrium constant for the reaction
below? AgBr(s) Ag+(aq) + Br–(aq)
(1) 5.40 x 10–15 (2) 5.40 x 10–13 (3) 1.90 x 10–8 (4) 7.35 x 10–7 (5) 1.90 x 10–6
