Visualizing and Interpreting Rate Expressions and Reaction Order from Data Tables

Q1. What does the expression $\frac{\Delta[SO_2]}{\Delta t}$ represent in chemical kinetics?

Background

Topic: Reaction Rates and Rate Expressions

This question is about interpreting the meaning of a rate expression in terms of the change in concentration of a reactant ($SO_2$) over time. Understanding how to write and interpret these expressions is fundamental in chemical kinetics.

Key Terms and Formulas:

• $\Delta[SO_2]$ = Change in concentration of $SO_2$ (in mol/L)

• $\Delta t$ = Change in time (in seconds, s)

• Rate of reaction = $\frac{\Delta[\text{Reactant or Product}]}{\Delta t}$

Step-by-Step Guidance

1. Recognize that $\frac{\Delta[SO_2]}{\Delta t}$ describes how the concentration of $SO_2$ changes with time during a reaction.

2. Recall that for a reactant, this value is typically negative because the concentration decreases as the reaction proceeds.

3. Understand that this expression gives the average rate of change over a time interval $\Delta t$.

Try solving on your own before revealing the answer!

Q2. Given the following data table, determine the order of the reaction with respect to [A]:

Background

Topic: Determining Reaction Order from Initial Rates

This question tests your ability to use experimental data to deduce the order of a reaction with respect to a single reactant. This is a key skill in chemical kinetics.

Key Terms and Formulas:

• Rate law: $\text{Rate} = k[A]^n$

• Order ($n$): The exponent that shows how the rate depends on the concentration of $A$.

Step-by-Step Guidance

1. Compare how the initial rate changes as $[A]$ increases. For example, when $[A]$ doubles, what happens to the rate?

2. Calculate the factor by which $[A]$ changes and the corresponding factor for the rate.

3. Relate the change in rate to the change in $[A]$ using the general rate law: $\text{Rate} \propto [A]^n$.

4. Set up the equation $\frac{\text{Rate}_2}{\text{Rate}_1} = \left(\frac{[A]_2}{[A]_1}\right)^n$ and solve for $n$ (but do not finish the calculation yet).

Try solving on your own before revealing the answer!