A base is a chemical which reacts with an acid forming water and salt only. Is this definition of base true? If true, metal carbonates are not considered as base (carbon dioxide is also formed during neutralization which violates the definition). Hence, the solution of metal carbonates are not considered to be alkalis (since alkali is a subset of base). However, metal carbonates are usually basic, e.g. sodium carbonate. I am bewildered whether we can call sodium carbonate a base then. Moreover, I would like to know the chemical reaction of sodium carbonate representing the production of OH- ions. Thanks very much.