Page No 183: - Chapter 7 P Block Elements Intext Solutions class 12 ncert solutions Chemistry - SaraNextGen [2024-2025]

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On April 24, 2024, 11:35 AM

Question 7.13:

List the important sources of sulphur.

Answer:

Sulphur mainly exists in combined form in the earth’s crust primarily as sulphates [gypsum (CaSO₄.2H₂O), Epsom salt (MgSO₄.7H₂O), baryte (BaSO₄)] and sulphides [(galena (PbS), zinc blends (ZnS), copper pyrites (CuFeS₂)].

Question 7.14:

Write the order of thermal stability of the hydrides of Group 16 elements.

Answer:

The thermal stability of hydrides decreases on moving down the group. This is due to a decrease in the bond dissociation enthalpy (H−E) of hydrides on moving down the group.

Therefore,

Question 7.15:

Why is H₂O a liquid and H₂S a gas?

Answer:

H₂O has oxygen as the central atom. Oxygen has smaller size and higher electronegativity as compared to sulphur. Therefore, there is extensive hydrogen bonding in H₂O, which is absent in H₂S. Molecules of H₂S are held together only by weak van der Waal’s forces of attraction.

Hence, H₂O exists as a liquid while H₂S as a gas.