Question

NAME: DATE: Post-Laboratory Assignment Points: 1. How are the rates of disappearance of l and Bros related? 2. Explain how and why a decrease in reactant concentration will affect the rate of a chemical reaction? 3. From the activation energy and A you determined in this experiment, calculate the rate constant k at 70°C 4. Would your observed reaction rates for the experiment have changed if you had doubled the volume of each solution used in the experiment

Answer 1

Question 1.

Reaction: BrO₃^- + 6I^- + 6H⁺ ----> Br^- + 3I₂ + 3H₂O

-d[BrO₃^-]/dt = -1/6 d[I^-]/dt = -1/6 d[H⁺]/dt

i.e. 6 d[BrO₃^-]/dt = d[I^-]/dt = d[H⁺]/dt

Question 2.

The rate of a chemical reaction is directly proportional to the concentration of reactant if it is a first-order reaction.

The rate of a chemical reaction is directly proportional to the square of the concentration of reactant if it is a second-order reaction

The rate of a chemical reaction is directly proportional to the cube of the concentration of reactant if it is a third-order reaction.

i.e. rate $\propto$ [reactant]ⁿ, where 'n' is the order of the reaction.

Question 3.

You have to use the Arrhenius equation, as shown below.

ln(k2/k1) = Ea/R (1/T1 - 1/T2)

Where k1, k2 are the rate constants at the temperatures T1 and T2, respectively.

Ea is the activation energy of the reaction.

Question 4.

The rate of reaction decreases.

For example, the reaction is of first-order, then the rate of reaction decreases by half.