You are provided with two reagent bottles marked A and B. One contains NH₄OH solution and the other contains NaOH solution. How will you identify them by a chemical test?

(a) What do you understand by amphoteric oxide?

(b) Give the balanced equations for the reaction with two different amphoteric oxides with a caustic alkali.

(c) Name the products formed.

On adding dilute ammonia solution to a colourless solution of a salt, a white gelatinous precipitate appears. This precipitate however dissolves on addition of excess of ammonia solution.

(a) From the following list, identify which metal salt solution was used above?
    Na, Al, Zn, Pb, Fe

(b) What is the formula of the white gelatinous precipitate obtained?

(c) Give the balanced equation(s) when sulphate of this metal reacts with ammonia solution in excess.