When acid reacts with base, it forms salt and water and the reaction is called as neutralization. These reactions are exothermic.
Acid + Base → Water + Salt
Examples:
Strong acid vs strong base
HCl + NaOH → H2O + NaOH
Strong acid vs weak base
H2SO4 + NH3 → NH4+ + SO42-
Weak acid vs strong base
CH3COOH + NaOH → NaOOCCH3 + H2O
Weak acid vs. weak base
CH3COOH + NH3 → CH3CONH2 + H2O