Question

Which reaction occurs most rapidly at standard conditions?

Answer 1

Answer : Option A) $H_{2}_{(g)} + I_{2}_{(s)} ----> 2HI_{(g)}$.

Explanation : The reaction of hydrogen gas with iodine in solid phase will react most rapidly at standard conditions.

A rapid chemical reaction is one where reactants react fast with each other to give the products at the standard temperature and pressure conditions.

In the given choices Iodine is highly reactive as it belongs to the halogen group and also atomic hydrogen is very reactive in nature, when both combine it gives hydrogen iodide which is much stable in nature than the reactants.

when one mole of hydrogen reacts with one mole of iodine it produces 2 moles of hydrogen iodide.

$H_{2}_{(g)} + I_{2}_{(s)} ----> 2HI_{(g)}$.

Answer 2

The reaction occurs most rapidly at standard conditions are:
H2(g) + I2(s) 2HI(g)

The reaction that do not occur rapidly at standard conditions are 
Cu(s) + S(s) CuS(s)
C6H12O6(s) + 6O2(g) 6CO2(g) + 6H2O(g)
5C2O42-(aq) + 2MnO4-(aq) + 16H+(aq) 10CO2(g) + 2Mn2+(aq) + 2H2O(l)
Ag+(aq) + I-(aq) AgI2(s)