What is the term used for the minimum kinetic energy required for the reactant molecules to undergo a chemical reaction?

For the reaction of $H_2$ with $I_2$,the rate constant is $2.5 \times 10^{-4} \ dm^3 \ mol^{-1} \ s^{-1}$ at $327 \ ^oC$ and $1.0 \ dm^3 \ mol^{-1} \ s^{-1}$ at $527 \ ^oC$. The activation energy for the reaction,in $kJ \ mol^{-1}$ is: $(R = 8.314 \ J \ K^{-1} \ mol^{-1})$

Consider an endothermic reaction $X \to Y$ with the activation energies $E_b$ and $E_f$ for the backward and forward reactions,respectively. In general:

The minimum energy that reactant molecules must possess at the time of collision for an effective collision is called ...

Why does the rate of a reaction increase with a rise in temperature?

For a reaction taking place in three steps at the same temperature,the overall rate constant is $K = \frac{K_1 K_2}{K_3}$. If $E_{a1}$,$E_{a2}$,and $E_{a3}$ are $40 \ kJ/mol$,$50 \ kJ/mol$,and $60 \ kJ/mol$ respectively,the overall activation energy $E_a$ is . . . . . . $kJ/mol$.