p-Block Elements (Group 15–18)

The variation of the boiling points of the hydrogen halides is in the order HF > HI > HBr > HCl. What explains the higher boiling point of hydrogen fluoride?

1. There is strong hydrogen bonding between HF molecules.
2. The bond energy of HF molecules is greater than in other hydrogen halides.
3. The effect of nuclear shielding is much reduced in fluorine which polarises the HF molecule.
4. The electronegativity of fluorine is much higher than for other elements in the group.

Which of the statements given below is incorrect?

1. O3 molecule is bent.
2. ONF is isoelectronic with O2N-
3. OF2 is an oxide of fluorine.
4. Cl2O7 is an anhydride of perchloric acid.

Nitrogen dioxide and sulphur dioxide have some properties in common. Which property is shown by one of these compounds, but not by the other?

1. Is soluble in water.
2. Is used as a food preservative.
3. Forms 'acid-rain'.
4. Is a reducing agent.

Acidity of diprotic acids in aqueous solutions increases in the order

1. H2S < H2Se < H2Te
2. H2Se < H2S < H2Te
3. H2Te < H2S < H2Se
4. H2Se < H2Te < H2S

Which is the strongest acid in the following?

1. HClO4
2. H2SO3
3. H2SO4
4. HClO3

Roasting of sulphides gives the gas X as a byproduct. This is a colourless gas with choking smell of burnt sulphur and causes great damage to respiratory organs as a result of acid rain. Its aqueous solution is acidic, acts as a reducing agent and its acid has never been isolated. The gas X is

1. CO2
2. SO3
3. H2S
4. SO2

Identify the incorrect statement, regarding the molecule XeO4:

1. XeO4 molecule is square planar.
2. There are four p -d bonds.
3. There are four sp3-p, bonds.
4. XeO4 molecule is tetrahedral.

In which of the following arrangements the given sequence is not strictly according to the property indicated against it?

1. HF < HCl < HBr < HI : increasing acidic strength
2. H2O < H2S < H2Se < H2Te : increasing pKa values
3. NH3 < PH3 < AsH3 < SbH3 : increasing acidic character
4. CO2 < SiO2 < SnO2 < PbO2 : increasing oxidising power

Which of the following statements is not valid for oxoacids of phosphorus?

1. Orthophosphoric acid is used in the manufacture of triple superphosphate.
2. Hypophosphorous acid is a diprotic acid.
3. All oxoacids contain tetrahedral four coordinated phosphorus.
4. All oxoacids contain at least one P=O unit and one P-OH group.

Sulphur trioxide can be obtained by which of the following reactions?

1. CaSO4 + C
2. Fe2(SO4)3
3. S + H2SO4
4. H2SO4 + PCl5