- They react with metals higher than hydrogen in the electrochemical series to liberate hydrogen. 2HCI + Zn(s) ZnCL2(ag) + H2(g)
- They react with bases to form salt. HCl(ag) + NaOH NacL(ag) + H2O(L)
- They liberate CO from trioxocarbonates. 2HCI(ag) + CaCO3(ag) CaCL2(ag) + H2O(L)