Question

A metal $X$ forms a salt $XS{O_4}$. The salt $XS{O_4}$ forms a clear solution in water which reacts with sodium hydroxide solution to form a blue precipitate $Y$. Metal $X$ is used in making electric wires and alloys like brass
$(a)$ What do you think metal $X$ could be?
$(b)$ Write the name, formula and color of salt $XS{O_4}$.
$(c)$ What is the blue precipitate $Y$?
$(d)$ Write a chemical equation of the reaction which takes place when salt $XS{O_4}$reacts with sodium hydroxide solution. Give the state symbol of all the reactants and products which occur in the above equation.

Answer 1

Hint: The metal forms the salt of sulphate. That means an acid is reacted with base in favorable condition forming a salt of sulphate. We also need to keep in mind that while reacting with sodium hydroxide it forms a blue precipitate, and the metal is used in making alloy like brass.

Complete answer:
$(a)$ The metal $X$ is Copper $(Cu)$ forming the salt $CuS{O_4}$ in water. Copper is soft, malleable and ductile metal with a very high thermal and electrical conductivity. Brass is an alloy of copper and zinc. It is used in decorating materials.
$(b)$ The name of salt $XS{O_4}$ is copper sulphate, the formula of salt is $CuS{O_4}$ and the color of salt is blue. The hydrated copper sulphate is blue as it is attached to the water molecule $CuS{O_4}.5{H_2}O$. This becomes white when anhydrous when it is not bound with water.
$(c)$ The blue precipitate $Y$ is copper hydroxide $Cu{(OH)_2}$. Hydroxide ion $(O{H^ - })$ binds to the $C{u^{2 + }}$ ions even more strongly than water does. As a result, hydroxide ion can displace water from the $C{u^{2 + }}$ ion, yielding copper hydroxide a blue precipitate.
$(d)$$CuS{O_4}(aq) + 2NaOH(aq) \to Cu{(OH)_2}(s) + N{a_2}S{O_4}(aq)$
Copper sulphate solution reacts with two moles of sodium hydroxide to form a blue precipitate of copper hydroxide and sodium sulphate.

Note:
Copper sulphate is used to kill molds in paints. It can be used to color ceramic. It can be used as a catalyst. Copper sulphate solution is blue but when we immerse an iron nail in the solution of copper sulphate then iron displaces copper from the solution of copper sulphate because iron is more reactive than copper changing the solution color from blue to green. Copper sulphate changes color when the higher reactive element than copper is reacted with it.