# Which of the following statements states the terms ' activity ' and ' selectivity ' respectively ?

(a) ability of catalyst to increase the chemical reaction ; ability of catalyst to decrease the reaction . (b) ability of catalyst to decrease the reaction ; ability of catalyst to direct the reaction to give particular products. (c) ability of catalyst to decrease the reaction ; ability of catalyst to reverse the reaction to give particular products . (d) ability of catalyst to increase the chemical reaction ; ability of catalyst to direct the direction the reaction to give particular products

Answer : ability of catalyst to increase the chemical reaction ; ability of catalyst to direct the direction the reaction to give particular products
Explanation :
Activity means the ability of catalyst to increase the chemical reaction .
A common example of activity is the reaction $\;H_{2}\;$ and $\;O_{2}\;$ to form water in the presence of platinum . Without the presence of the catalyst , the mixture of $\;H_{2}\;$ and $\;O_{2}\;$ can be safely stored . But in the presence of catalyst , the reaction occurs with explosive voilence .
The selectivity means the ability of the catalyst to direct reaction to give particular products .
For example , n - heptane in the presence of platinum catalyst gives toulene .
$nC_{7}H_{16} \quad \underrightarrow{pt} \quad C_{6}H_{5}CH_{3}$