Answer:
15 seconds
Explanation:
The given parameters for the experiment are;
The time it takes the solution to change from a clear color to a bluish-purple color at a given temperature = 30 seconds
The temperature at which Sally replicates the experiment with the same solution = 10°C higher than the temperature the experiment was carried out by John
Given that the process involves a change in color, which is a characteristic of a chemical reaction, and that the rate of a chemical reaction increases as the temperature of the reacting system is increased, we have time it takes for the solution to change color at a temperature increased by 10°C, will be a time lesser than 30 seconds