Equation for chemical Reaction: H2 + Cl2 --> 2HCl.?

The same number of moles of H2 and Cl2 will be used up because they have the same coefficient in the balanced chemical reaction. There is less Cl2 present than H2, so it will all get used up. However, this will only be enough to use up 1.5 moles of H2, so .5 moles of H2 will remain after the reaction is complete. 3 moles of HCl will be present after the reaction because twice the number of moles of HCl must be formed than Cl2 is used up because the coefficient of HCl is double that of Cl2 in the balanced reaction.