What is the value of electron gain enthalpy of Na if IE₁ of Na = 5.1 eV?

• -5.1 eV

• -10.2 eV

• +2.55 eV

• +10.2eV

32.

Assertion (A): K, Rb and Cs form superoxides.

Reason (R): The stability of the superoxides increases from 'K' to 'Cs' due to decrease in lattice energy.

The correct answer is

• Both (A) and (R) are true and (R) is the correct explanation of (A).

• Both (A) and (R) are true but (R) is not the correct explanation of (A)

• (A) is true but (R) is not true

• (A) is not true but (R) is true

Which one of the following order is correct for the first ionisation energies of the elements?

• B <Be <N < O

• Be <B <N < O

• B <Be <O <N

• B <O <Be <N

The oxidation number of oxygen in KO₃, Na₂O₂ is

• 3, 2

• 1, 0

• 0, 1

• -0.33, -1

What is the fuel of atomic pile ?

• Thorium

• Sodium

• Uranium

• Petroleum

The maximum number of unpaired electrons is present in

• Fe

• Cu

• Co

• Ni

The pair, that is referred as 'chemical twins' is

• Ac, Cf

• Hf, Ta

• Tc, Re

• La, Ac

Ce⁴⁺ is stable. This is because of

• half-filled d-orbitals

• all paired electrons ind-orbitals

• empty orbital

• fully filled d-orbital

What is the orbital angular momentum of an electron in 'f'  orbital?

• $\frac{1.5\mathrm{h}}{\mathrm{\pi }}$

• $\frac{\sqrt{6}\mathrm{h}}{\mathrm{\pi }}$

• $\frac{\sqrt{3}\mathrm{h}}{\mathrm{\pi }}$

• $\frac{\sqrt{3}\mathrm{h}}{2\mathrm{\pi }}$

Fool's gold is

• Cu₂S

• FeS₂

• Al₂O₅

• CuFeS₂