Q: For the reaction $$\mathrm{N_2$ + 3H_2 \rightarrow 2NH_3}$$, the rate of disappearance of $$\mathrm{H_2$} is$$ $$1.67 \times 10$$^{-4}$$\ \mathrm{mol\ L$$^{-1}$$\ s$$^{-1}$$}. $$What is the rate of formation of $$\mathrm{NH_3$}$$?

$$1.11 \times 10$$^{-4}$$\ \mathrm{mol\ L$$^{-1}$$\ s$$^{-1}$$}$$

Question 1

Which of the following best describes the rate law for the reaction $$\mathrm{C_2H_4Br_2 + 3I^- \rightarrow C_2H_4 + 2Br^- + I_3$^-}$$, based on experimental data showing that doubling $$[\mathrm{C_2H_4Br_2}] or$$ $$[\mathrm{I^-}]$$ each doubles the initial rate?

Accepted Answer

$$r = k[\mathrm{C_2H_4Br_2}][\mathrm{I^-}]$$

Question 2

For a first-order reaction $$\mathrm{X \rightarrow Z}$$, which integrated rate law correctly describes the concentration of X as a function of time?

Accepted Answer

$$[X]_t = [X]_0 e$$^{-kt}$$

Question 3

A reaction is found to be second order in X. Which plot will yield a straight line?

Accepted Answer

$$\dfrac{1}{[X]} vs$$. $$t$$

Question 4

The decomposition of $$\mathrm{NO_2$} at 300$$°C is monitored. A plot of $$\ln[NO_2$] vs$$. $$t is $$not linear, but a plot of $$1/[NO_2$] vs$$. $$t is $$linear. What is the order of the reaction with respect to $$\mathrm{NO_2$}$$?

Accepted Answer

Second order

Question 5

Which factor does NOT generally increase the rate of a chemical reaction?

Accepted Answer

Decreasing the available surface area of a solid reactant

Question 6

For the reaction $$\mathrm{N_2$ + 3H_2 ightarrow 2NH_3}$$, the rate of disappearance of $$\mathrm{H_2$} is$$ $$1.67 	imes 10$$^{-4}$$\ \mathrm{mol\ L$$^{-1}$$\ s$$^{-1}$$}. $$What is the rate of formation of $$\mathrm{NH_3$}$$?

Accepted Answer

$$1.11 	imes 10$$^{-4}$$\ \mathrm{mol\ L$$^{-1}$$\ s$$^{-1}$$}$$

Question 7

A reaction has the rate law $$r = k[X]. $$What are the units of the rate constant $$k$$?

Accepted Answer

$$\mathrm{s$$^{-1}$$}$$

Question 8

Which statement about the relationship between the rate law and the stoichiometric equation is correct?

Accepted Answer

The rate law must be determined experimentally and is not directly deducible from the stoichiometric equation.

Question 9

In a real-world scenario, why does rusting of iron (corrosion) proceed faster in humid, salty environments?

Accepted Answer

Because the presence of water and salt increases the concentration of reactants and provides a better medium for electron transfer.

Question 10

A catalyst increases the rate of a reaction by:

Accepted Answer

Lowering the activation energy of the reaction

Question 11

For a zero-order reaction, which of the following is true?

Accepted Answer

The rate is independent of the concentration of reactant.

Question 12

In the SN2 reaction mechanism, the rate depends on:

Accepted Answer

The concentrations of both the nucleophile and the substrate

Question 13

Which graphical method would you use to determine if a reaction is first order with respect to a reactant X?

Accepted Answer

Plot $$\ln[X] vs$$. $$t$$ and look for a straight line

Question 14

If the rate law for a reaction is $$r = k[X][Y]$$, what is the overall order of the reaction?

Accepted Answer

Second order

Question 15

A reaction has a rate law $$r = k[X]^2. If $$the initial concentration of X is doubled, by what factor does the initial rate increase?

Accepted Answer

It quadruples

Question 16

Which of the following statements about the rate constant $$k is $$correct?

Accepted Answer

It depends on the temperature and the specific reaction.

Question 17

In a reaction $$A \rightarrow B$$, the concentration of A decreases from 0.200 M to 0.153 M in 50.0 seconds. What is the average rate of disappearance of A over this interval?

Accepted Answer

$$4.7 	imes 10$$^{-4}$$\ \mathrm{mol\ L$$^{-1}$$\ s$$^{-1}$$}$$

Question 18

Which of the following best explains why the rate of a reaction generally increases with temperature?

Accepted Answer

The reactants have higher kinetic energy, leading to more frequent and energetic collisions.

Question 19

A reaction is found to be first order in X and zero order in Y. Which rate law is correct?

Accepted Answer

$$r = k[X]$$

Reaction Kinetics in Organic Chemistry: Study Notes

Guida di studio - Domande di pratica

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