Answer : The number of moles of
required are, 0.6 mole.
Explanation : Given,
Moles of HI = 1.2 moles
The given balanced chemical reaction is,

From the balanced chemical reaction, we conclude that
As, 2 moles of
react with 1 mole of

So, 1.2 moles of
react with
mole of

Therefore, the number of moles of
required are, 0.6 mole.