What is the role of a catalyst in a catalytic reaction?

Explain the effect of an increase in temperature on the rate of reaction and the rate constant.

In a laboratory,a biochemical reaction performed outside the human body in the absence of an enzyme proceeds at a rate $10^{-6}$ times slower. If this reaction is performed in the presence of an enzyme,what will be the activation energy of the reaction?

For a gaseous reaction,a large increase in the rate of reaction with a small increase in temperature indicates:

Fill in the blank :
$1.$ In collision theory the molecules are hard .........
$2.$ In a reality the molecules are hard ..........
$3.$ Collision take place with .......... species.

In the plot of $\ln k$ versus $\frac{1}{T}$,what do the slope and intercept represent?