Final answer:
The reaction rate indeed doubles for every 10 °C rise in temperature, leading to a fourfold increase at a 20 °C rise and 128 times faster at a 70 °C rise. Decomposition that would normally take 48 minutes will only take 12 minutes with a 20 °C increase in temperature. Therefore, the correct option is a).
Step-by-step explanation:
The question relates to how the rate of a chemical reaction can change with a temperature change, specifically stating that the rate doubles with every 10 °C rise. When the temperature is raised from 25 °C to 45 °C, which is a 20 °C increase, the reaction rate increases fourfold (double for the first 10 °C and then double again for the next 10 °C).
For the scenario where the temperature goes from 25 °C to 95 °C, the rate increases 27 times because there is a 70 °C difference. This is because the reaction rate doubles for each 10 °C. The calculation is 2 x 2 x 2 x 2 x 2 x 2 x 2 (or 128 times faster).
If a sample of NaClO3 is 90% decomposed in 48 minutes at a certain temperature, increasing the temperature by 20 °C would double the rate twice, making it four times quicker. Therefore, the decomposition would take approximately 48/4, which is 12 minutes. In conclusion, the reaction rate increase depends on the total temperature increase and follows an exponential pattern due to each 10 °C increment leading to a doubling in rate. Therefore, part (a) of the question is true.