When sulphuric acid is added to a salt solution, it will react with the salt to form sulphate and hydrogen ions. The reaction is as follows:
H2SO4 + NaCl —> NaHSO4 + HCl
This reaction is highly exothermic, meaning that it releases a large amount of heat energy. As a result, the solution may become very hot and can cause severe burns if it comes into contact with skin.