In a reaction,the rate of reaction doubles with a $10^\circ C$ rise in temperature. If the temperature is increased from $10^\circ C$ to $100^\circ C$,by how many times will the rate of reaction increase?

Oxygen is available in plenty in air,yet fuels do not burn by themselves at room temperature. Explain.

The reaction: $Cr_{2}O_{3} + 2 Al \rightarrow Al_{2}O_{3} + 2 Cr$ $\quad (\Delta_{r}G^{\Theta} = -421 \ kJ)$ is thermodynamically feasible as is apparent from the Gibbs energy value. Why does it not take place at room temperature?

$A$ reaction takes place in three steps with individual rate constants and activation energies. The overall rate constant is given by $k = (\frac{k_1 k_2}{k_3})^{2/3}$. The overall activation energy of the reaction in $kJ/mol$ is:

$Step$	$Rate\ Constant\ /\ Activation\ energy$
$Step\ 1$	$k_1, E_{a_1} = 180\ kJ/mol$
$Step\ 2$	$k_2, E_{a_2} = 80\ kJ/mol$
$Step\ 3$	$k_3, E_{a_3} = 50\ kJ/mol$

The activation energy for a reaction which doubles the rate when the temperature is raised from $298 \ K$ to $308 \ K$ is ........... $kJ \ mol^{-1}$

Which one of the following is true for an exothermic reaction $A \rightleftharpoons B$, if $E_f$ and $E_b$ are the activation energies of forward and backward reactions respectively?