51.

The correct discending order of oxidising power of the following is

• ${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-} > {\mathrm{MnO}}_4^{-} > {\mathrm{VO}}_2^{+}$

• ${\mathrm{MnO}}_4^{-} > {\mathrm{Cr}}_2{\mathrm{O}}_7^{2-} > {\mathrm{VO}}_2^{+}$

• ${\mathrm{VO}}_2^{+} > {\mathrm{MnO}}_4^{-} > {\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}$

• ${\mathrm{MnO}}_4^{-} > {\mathrm{VO}}_2^{+} > {\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}$

The number of electrons that are involved in the reduction of permanganate to manganese (II) salt, manganate and manganese dioxide respectively are

• 5, 1, 3

• 5, 3, 1

• 2, 7, 1

• 5, 2, 3

The ionisation enthalpy of He⁺ ion is 19.60 10^-18 J atom^-1. The ionisation enthalpy of Li²⁺ ion will be

• 84.2 × 10^-18 J atom^-1

• 44.10 × 10^-18 J atom^-1

• 63.20 × 10^-18 J atom^-1

• 21.20 × 10^-18 J atom^-1

Among the elements B, Mg, Al and K the correct order of increasing metallic character is

• B < Al < Mg < K

• B < Mg < Al < K

• Mg < B < Al < K

• Mg < Al < B < K

Which one of the following is an amphoteric oxide?

• Mn₂O₇

• CrO

• V₂O₄

• Cr₂O₃

Molecules/ ions and their magnetic properties are given below-

Molecule/ Ion	Magnetic Property
i. C6H6	1. Antiferromagnetic
ii. CrO2	2. Ferrimagentic
iii. MnO	3. Ferromagnetic
iv. Fe3O4	4. Paramagnetic
v. Fe3+	5. Diamagnetic

The correctly matched pairs in the above is

• i - 5; ii - 3; iii - 2; iv - 1; v - 4

• i - 3; ii - 5; iii - 1; iv - 4; v - 2

• i - 5; ii - 3; iii - 1; iv - 2; v - 4

• i - 5; ii - 3; iii - 1; iv - 4; v - 2

Among the following, the element of highest first ionisation enthalpy is

• C

• Ne

• Be

• N

Arrange the following in the order of increasing mass (atomic mass O = 16, Cu = 63, N = 14)

I. One atom of oxygen

II. One atom of nitrogen

III. 1 × 10^-10 mole of oxygen

IV. 1 × 10^-10  mole of copper

• II < I < III < IV

• I < II < III < IV

• III < II < IV < I

• II < IV < I < III

The correct decreasing order of first ionisation enthalpies of five elements of the second period is

• Be > B > C > N > F

• N > F > C > B > Be

• F > N > C > Be > B

• N > F > B > C > Be

The first () and second (ΔH₂) ionisation enthalpies (in kJ mol^-1) and the (Δ_egH) electron gain enthalpy (in kJ mol^-1) of the elements I, II, III, IV and V are given below

Element	ΔH1	ΔH2	ΔegH
I	520	7300	-60
II	419	3051	-48
III	1681	3374	-328
IV	2372	5251	+48

The most reactive metal and the least reactive non-metal of these are respectively

• I and IV

• IV and II

• II and IV

• III and IV