a) will increase
greater collision energy
so greater chance of activation energy being exceeded
so greater fraction of successful collisions
k increases
b) will increase
more particles per unit volume
so collision frequency increases
k unchanged
c) will increase
more particles per unit volume
so collision frequency increases
k unchanged
d) will increase
alternative reaction pathway
so lower activation energy
so greater fraction of successful collisions
(k increases unless catalyst in rate equation in which case k unchanged)