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General Chemistry Exam 1 Review – Kinetics and Equilibrium Guidance

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Q26. The rate law for the reaction A + B → C is rate = ________.

Background

Topic: Chemical Kinetics – Rate Laws

This question tests your ability to determine the rate law for a reaction using experimental data. The rate law expresses how the rate depends on the concentrations of reactants.

Table of concentrations and initial rates for A and B

Key Terms and Formulas:

  • Rate Law:

  • k = rate constant

  • m, n = reaction orders with respect to A and B

Step-by-Step Guidance

  1. Compare experiments where only one reactant's concentration changes to determine the order for each reactant.

  2. For [A], compare experiment 1 and 3 (B is constant):

  3. For [B], compare experiment 1 and 2 (A is constant):

  4. Set up the ratios and solve for m and n (reaction orders) using the data from the table.

  5. Once you have the orders, write the rate law in the form .

Try solving on your own before revealing the answer!

Final Answer: rate = k[A]^2[B]

By comparing the rates and concentrations, you find that the reaction is second order in A and first order in B. The rate law is .

This matches answer choice C.

Q27. Which graph shows the correct relationship between concentration and time for a reaction that is second order in [A]?

Background

Topic: Chemical Kinetics – Integrated Rate Laws

This question tests your ability to recognize the graphical representation of a second-order reaction with respect to [A].

Key Terms and Formulas:

  • Second-order integrated rate law:

  • For a second-order reaction, a plot of vs. time is linear.

Step-by-Step Guidance

  1. Recall the integrated rate law for second-order reactions.

  2. Identify which plot (from the provided images) would be linear according to the second-order law.

  3. Compare the options: vs. time, vs. time, vs. time, etc.

  4. Look for the graph where increases linearly with time.

Graph of 1/[A] vs. time

Try solving on your own before revealing the answer!

Final Answer: The correct graph is the one where 1/[A] increases linearly with time (Image 4).

This is characteristic of a second-order reaction. The plot of vs. time is a straight line.

Q37. Which of the following expressions is the correct equilibrium-constant expression for the equilibrium between dinitrogen tetroxide and nitrogen dioxide?

Background

Topic: Chemical Equilibrium – Equilibrium Constant Expressions

This question tests your ability to write the equilibrium constant expression for a given chemical equation.

Reaction:

Key Terms and Formulas:

  • Equilibrium constant ():

  • For the reaction ,

Step-by-Step Guidance

  1. Write the balanced chemical equation.

  2. Recall the general form for :

  3. Apply the coefficients from the balanced equation to the expression.

  4. Identify the correct formula from the provided options and images.

Equilibrium constant expression [NO2]^2/[N2O4]

Try solving on your own before revealing the answer!

Final Answer: (Image 7)

This is the correct equilibrium constant expression for the reaction .

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