# Why is only one proton transferred in the reaction between sulfuric acid and sodium chloride

$$\ce{NaCl + H2SO4 -> NaHSO4 + HCl}$$

The above reaction happens, but why doesn't the following happen? Or does it but only when one of the reactants is in excess?

$$\ce{2NaCl + H2SO4 -> Na2SO4 + 2HCl}$$

The second reaction seems plausible to me. How can I predict whether a similar type of reaction will be like the first equation or the second equation?

• The first reaction takes place when sulfuric acid is concentrated. – Binary Geek Mar 24 '15 at 18:19
• – Mithoron Mar 24 '15 at 21:15