# A chemist runs a reaction at 65°C and determines its rate to be 0.000364 M/s. If she decreases the temperature to 25°C, what will the rate of the reaction be?

##### 1 Answer

#### Answer:

Here's what I get.

#### Explanation:

There are two ways to approach this problem.

**A. Use a rule of thumb**

A **rule of thumb** states that the rate of a reaction changes by a factor of two for every 10 °C change in temperature.

You are decreasing the temperature from 65 °C to 25 °C, a decrease of 40 °C.

Thus, the new rate will be

**B. Use the Arrhenius equation**

Ideally, you would know the activation energy

Then you could use the **Arrhenius equation** to calculate the rate at the new temperature.

#color(blue)(bar(ul(|color(white)(a/a)ln(k_2/k_1) = E_"a"/R(1/T_1 -1/T_2)color(white)(a/a)|)))" "# where

Since you are changing only the temperatures, the rates are directly proportional to the rate constants, and we can write:

#ln(r_2/r_1) = E_"a"/R(1/T_1 -1/T_2)#

Let's assume that the activation energy is