Question

A black coloured compound X turns to brown metal Y when reacts with hydrogen gas. Y
cannot liberate H2 gas with dil. HCl.
i) Identify X and Y and write the chemical equation for that reaction.
ii) Mention the type of reaction which has taken place.
iii) When Y is added to two test tubes containing ZnSO4 solution in one test tube and
AgNO3 solution in another test tube, in which test tube reaction takes place. Write
the chemical equation for that reaction.

Answer 1

Answer is in the image

hope it helps you:)

Answer 2

When a black coloured CuO reacts with hydrogen gas, it results in formation of brown Cu ( Copper) metal. Hence, Cu cannot liberate H2 gas with dilute HCl.

i) Here, X is Copper (II) oxide (CuO) and Y is Copper (Cu).

The required chemical reaction is -:

CuO (aq) + H2(g) → Cu(s) + H2O(l)

ii) The type of reaction which has taken place are -

displacement and redox reaction.

• Redox reaction : The reaction in which oxidation and reduction takes place simultaneously.

• In redox reaction, the change in oxidation states of atoms take place.

• Oxidation involves loss of hydrogen or loss of electrons.

• Reduction involves loss of oxygen, loss of electrons or addition of hydrogen.

• Displacement reaction : It is a chemical reaction in which a more reactive element displaces a less reactive element from its compound.

• Displacement reactions are generally exothermic in nature.

iii) The reaction takes place in second test tube which contains AgNO3 solution whereas no reaction in first test tube.

• Cu + ZnSO4 → No reaction

• No reaction takes place because Cu is less reactive than Zn and hence, cannot displace Zn.

• Cu + AgNO3 → Cu(NO3) 2 + 2Ag

• Cu is more reactive than Ag and hence, it displaces Ag from AgNO3.