Q: Which of the following is the correct formula for calculating the heat ($$q) $$absorbed or released by a substance?

$$q = m \times c \times \Delta T$$

Q: Given the following data for the reaction $$2\ \mathrm{HBr} + \mathrm{Ca(OH)_2} \rightarrow \mathrm{$$CaBr_2$$} + 2\ \mathrm{H_2O} at 298 K$$: Exp 1: [HBr]=0.0025 M, [Ca(OH)2]=0.0050 M, Initial Rate=0.0221 M/s; Exp 2: [HBr]=0.0070 M, [Ca(OH)2]=0.0050 M, Initial Rate=0.0884 M/s; Exp 3: [HBr]=0.0035 M, [Ca(OH)2]=0.0100 M, Initial Rate=0.0221 M/s. What is the rate constant $$k if $$the reaction is second order with respect to HBr and zeroth order with respect to Ca(OH)2?

$$1.8 \times 10^3$\ \mathrm{M}^{-1}\mathrm{s}^{-1}$$

Question 1

Which of the following statements best describes the energy changes during the evaporation of water at 100°C?

Accepted Answer

Heat energy is transferred from the surroundings to the water.

Question 2

Given the reaction $$\mathrm{Ca(s) + 2H_2O(l) \rightarrow Ca$$^{2+}$$(aq) + 2OH^-(aq) + H_2$(g)}$$ and the following enthalpy values: $$\Delta H_f$$^{\circ}$$(Ca^{2+}) = -226.7$$\ \mathrm{kJ/mol}$$, $$\Delta H_$$f^{\circ}(OH^-) = -230.0$$\ \mathrm{kJ/mol}$$, $$\Delta H_$$f^{\circ}(H_2O) = -241.8$$\ \mathrm{kJ/mol}$$, $$\Delta H_$$f^{\circ}$$($$H_2) = 0$$\ \mathrm{kJ/mol}$$, what is $$\Delta $$H^{\circ}$ for the reaction?

Accepted Answer

$$-233.5\ \mathrm{kJ}$$

Question 3

Which of the following is the correct formula for calculating the heat ($$q) $$absorbed or released by a substance?

Accepted Answer

$$q = m 	imes c 	imes \Delta T$$

Question 4

If $$2\ \mathrm{H_2$(g) + O_2$(g) \rightarrow 2\ H_2O(l)}$$ has $$\Delta H = -483.6\ \mathrm{kJ}$$, how much enthalpy is released when $$1.77\ \mathrm{mol} of$$ $$\mathrm{H_2$} is $$combusted?

Accepted Answer

$$-340.0\ \mathrm{kJ}$$

Question 5

A cube of gallium metal ($$\mathrm{Ga}) $$melts in your hand at $$29.76^{\circ}$$\mathrm{C}$$. What is the sign of q$$_{\mathrm{Ga}}$$?

Accepted Answer

$$q_{\mathrm{Ga}} \u003e 0$$

Question 6

When $$4.25\ \mathrm{g} of$$ $$\mathrm{NH_4NO_3} is $$dissolved in $$60.0\ \mathrm{g} of $$water at $$22.0^{\circ}$$\mathrm{C}$$, the process removes 1.37$$\ \mathrm{kJ}$$ of energy from the solution. What is the final temperature of the solution? (c$$_{\mathrm{water}} = 4.184\ \mathrm{J/g\cdot K}$$)

Accepted Answer

$$15.0^{\circ}$$\mathrm{C}$$

Question 7

In general, as activation energy ($$E_a) $$increases, the rate constant ($$k) ____.$$

Accepted Answer

decreases

Question 8

For the reaction $$2\ \mathrm{NO} + \mathrm{O_2$} \rightarrow 2\ \mathrm{NO_2$}$$, which rate law matches the experimental data: Exp 1: [NO]=0.090 M, [O2]=0.050 M, Initial Rate=0.440 M/s; Exp 2: [NO]=0.090 M, [O2]=0.100 M, Initial Rate=0.440 M/s; Exp 3: [NO]=0.270 M, [O2]=0.050 M, Initial Rate=1.32 M/s?

Accepted Answer

Rate = k[NO]^2

Question 9

Which of the following would increase the rate of a reaction?

Accepted Answer

Increasing the concentration of reactants (for a 1st or 2nd order process).

Question 10

The half-life ($$t_{1/2}) of$$ $$\mathrm{N_2O_5} is$$ $$54.6\ \mathrm{s}$$ and its initial concentration is $$0.85\ \mathrm{M}. $$Which equation should be used to determine the rate constant ($$k) $$for a first-order reaction?

Accepted Answer

$$k = \dfrac{0.693}{t_{1/2}}$$

Question 11

Which of the following statements about reaction rates is correct?

Accepted Answer

The rate increases if the concentration of reactants is increased.

Question 12

For a reaction where $$A$$ and $$B$$ are reactants, which rate law matches a second-order reaction?

Accepted Answer

$$\mathrm{rate} = k[A][B]$$

Question 13

Given the following data for the reaction $$2\ \mathrm{HBr} + \mathrm{Ca(OH)_2} \rightarrow \mathrm{$$CaBr_2$$} + 2\ \mathrm{H_2O} at 298 K$$: Exp 1: [HBr]=0.0025 M, [Ca(OH)2]=0.0050 M, Initial Rate=0.0221 M/s; Exp 2: [HBr]=0.0070 M, [Ca(OH)2]=0.0050 M, Initial Rate=0.0884 M/s; Exp 3: [HBr]=0.0035 M, [Ca(OH)2]=0.0100 M, Initial Rate=0.0221 M/s. What is the rate constant $$k if $$the reaction is second order with respect to HBr and zeroth order with respect to Ca(OH)2?

Accepted Answer

$$1.8 	imes 10^3$\ \mathrm{M}^{-1}\mathrm{s}^{-1}$$

Question 14

Which of the following graphs best represents the relationship between concentration and time for a reaction that follows the rate law $$\mathrm{Rate} = k[A]$$?

Accepted Answer

A straight line with negative slope for $$\ln[A] vs. $$time.

Question 15

Consider the following reaction mechanism for the decomposition of $$\mathrm{Cl_2O}$$: Step 1: $$\mathrm{Cl_2O ightarrow Cl_2$ + O}$$, $$k_1 = 5.2$$ 	imes $$10^2$$; Step 2: $$\mathrm{Cl_2O + O ightarrow Cl_2$ + O_2$}$$, $$k_2 = 1.37$$ 	imes $$10^4. $$Which statement is true?

Accepted Answer

Step 1 is the slow step, and Step 2 is the fast step.

Question 16

As the temperature decreases, what happens to the rate constant ($$k) $$for a chemical reaction?

Accepted Answer

It decreases.

Question 17

Given the Arrhenius equation $$k = A e$$^{-E_a/(RT)}$$, which of the following changes will increase the rate constant k$?

Accepted Answer

Decrease the activation energy $$E_a.$$

Question 18

Which of the following is the correct expression for the change in internal energy ($$\Delta E) of a $$system?

Accepted Answer

$$\Delta E = q + w$$

Question 19

Which of the following statements about enthalpy ($$\Delta H) is $$correct?

Accepted Answer

A positive $$\Delta H$$ indicates an endothermic reaction.

Thermochemistry and Chemical Kinetics: Study Guide

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