p-Block Elements

Question 1

In potash alum, the ratio of K⁺ and SO₄²⁻ ions is

Accepted Answer

1 : 2. Potash alum is K₂SO₄·Al₂(SO₄)₃·24H₂O. One formula unit supplies 2 K⁺ ions and 4 sulphate ions — one from K₂SO₄ and three from Al₂(SO₄)₃ — so the ratio is 2 : 4, that is 1 : 2.

Answer

2 : 1

Answer

2 : 3

Answer

3 : 2

Question 2

The correct statement is

Accepted Answer

Boron has a maximum covalency of four.. Boron's valence shell is 2s and 2p only — four orbitals, no d — so it can form at most four bonds, as in BF₄⁻. Beryllium likewise has four valence orbitals, not three; aluminium has nine available once its 3d set is counted, not five; and magnesium can reach a covalency of six.

Answer

Beryllium has three valence orbitals.

Answer

Magnesium has a maximum covalency of four.

Answer

Aluminium has five valence orbitals.

Question 3

Given below are two statements. In the light of the above statements, choose the most appropriate answer from the options given below. Statement I: Like nitrogen that can form ammonia, arsenic can form arsine. Statement II: Antimony cannot form antimony pentoxide.

Accepted Answer

Statement I is correct but Statement II is incorrect. Statement I is correct: every group 15 element forms a trihydride, so arsenic gives arsine, AsH₃, just as nitrogen gives NH₃. Statement II is incorrect because antimony does form the pentoxide Sb₂O₅ — the +5 state is accessible to Sb, and it is bismuth where the +5 state becomes unstable owing to the inert pair effect.

Answer

Both Statement I and Statement II are correct

Answer

Both Statement I and Statement II are incorrect

Answer

Statement I is incorrect but Statement II is correct

Q1.In potash alum, the ratio of K⁺ and SO₄²⁻ ions is

Q2.The correct statement is

Q3.Given below are two statements. In the light of the above statements, choose the most appropriate answer from the options given below.