nH2=V(L)22.4=22.422.4=1 mol
nCl2=11.222.4=0.5 mol
H2(g)+Cl2(g)→2HCl(g)
initially - 1 mol 0.5 mol 0
Here, Cl2 is the limiting reagent. Thus Cl2 will decide the moles of HCl formed.
∴
Moles of HCl formed =21×0.5=1 mol
Hence, the correct answer is option (a).