Q: Given the following data for the concentration of a dye over time: at $$t=0$$ min, $$[Dye]=3.40 \times 10$$^{-6}$$ M; at t=1$ min, $$[Dye]=2.00 \times $$10^{-6} M. $$What is the average rate of reaction over the first minute?

$$1.40 \times 10$$^{-6}$$ mol/L\cdot min$

Question 1

A blue dye is oxidized with bleach, causing its color to fade over time as shown in the images. Which of the following best describes what is being measured in this experiment?

Accepted Answer

The rate of disappearance of the blue dye

Question 2

Given the following data for the concentration of a dye over time: at $$t=0$$ min, $$[Dye]=3.40 	imes 10$$^{-6}$$ M; at t=1$ min, $$[Dye]=2.00 	imes $$10^{-6} M. $$What is the average rate of reaction over the first minute?

Accepted Answer

$$1.40 	imes 10$$^{-6}$$ mol/L\cdot min$

Question 3

Which of the following statements about reaction rates is correct?

Accepted Answer

Rates are always positive and are calculated based on the change in concentration per unit time.

Question 4

For the reaction $$2 SO_2$(g) + O_2$(g) \rightarrow 2 SO_3$(g)$$, which of the following correctly relates the rates of disappearance and appearance?

Accepted Answer

$$-\frac{1}{2} \frac{\Delta [SO_2$]}{\Delta t} = -\frac{\Delta [O_2$]}{\Delta t} = \frac{1}{2} \frac{\Delta [SO_3$]}{\Delta t}$$

Question 5

A reaction is found to have a rate law $$Rate = k[A][B]^2. $$What is the overall order of the reaction?

Accepted Answer

Third order

Question 6

For a first-order reaction, which of the following plots will yield a straight line?

Accepted Answer

$$\ln [A] vs. $$time

Question 7

The half-life of a first-order reaction is given by which of the following equations?

Accepted Answer

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

Question 8

Which of the following best explains why increasing the temperature increases the rate of a chemical reaction?

Accepted Answer

It increases the number of collisions and the fraction of molecules with sufficient energy to overcome the activation energy barrier.

Question 9

The Arrhenius equation relates the rate constant $$k to $$temperature $$T as$$ $$k = Ae$$^{-E_a/RT}$$. If you plot $$\ln k$$ versus 1/T$, what does the slope of the line represent?

Accepted Answer

$$-E_a/R$$

Question 10

A catalyst increases the rate of a chemical reaction by:

Accepted Answer

Providing an alternative pathway with a lower activation energy

Question 11

For the reaction $$2 NO_2$(g) \rightarrow N_2O_4(g)$$, which of the following is the correct equilibrium constant expression in terms of concentrations?

Accepted Answer

$$K_c = \frac{[N_2O_4]}{[NO_2$]^2}$$

Question 12

If the equilibrium constant $$K$$ for a reaction is much less than 1, what does this indicate about the position of equilibrium?

Accepted Answer

The reaction is reactant-favored at equilibrium.

Question 13

For the reaction $$N_2(g) + 3$$ $$H_2(g$$) \rightleftharpoons 2 $$NH_3(g$$)$$, if the initial concentrations are $$[$$N_2$$]=0.20$$ M, $$[$$H_2$$]=0.20$$ M, and $$[$$NH_3$$]=0$$ M, and at equilibrium $$[$$NH_3$$]=0.013$$ M, what is the value of K_c$?

Accepted Answer

$$K_c = \frac{(0.013)^2$}{(0.1935)(0.1805)^3$}$$

Question 14

Which of the following changes will NOT affect the value of the equilibrium constant $$K$$ for a given reaction?

Accepted Answer

Adding a catalyst

Question 15

Which of the following best describes the effect of increasing the pressure by decreasing the volume for a gas-phase equilibrium?

Accepted Answer

The equilibrium shifts toward the side with fewer moles of gas.

Question 16

Which of the following is a correct Brønsted-Lowry acid-base pair?

Accepted Answer

NH$$_4^+$$ and NH$$_3$$

Question 17

A 0.1 M solution of HCl has a pH of:

Accepted Answer

1.0

Question 18

Which of the following is the correct relationship between $$K_a$$ and $$K_b$$ for a conjugate acid-base pair at 25°C?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 19

Which of the following salts will produce a basic solution when dissolved in water?

Accepted Answer

NaCH$$_3$$COO

Chemical Kinetics and Equilibrium: Rates, Mechanisms, and Acid-Base Chemistry

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