1
MCQ (Single Correct Answer)

NEET 2013 (Karnataka)

In which of the following ionization processes the bond energy increases and the magnetic behaviour changes from paramagnetic to diamagnetic.
A
O2 $$ \to $$ O2+
B
C2 $$ \to $$ C2+
C
NO $$ \to $$ NO+
D
N2 $$ \to $$ N2+

Explanation

Molecular orbital configuration of

O2+ $$ \Rightarrow $$ $$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}{\sigma ^*}2{s^2}\sigma 2p_z^2\pi 2p_y^2{\pi ^*}2p_x^1{\pi ^*}2p_y^1$$ $$ \Rightarrow $$ Paramagnetic

Bond order = $${{10 - 5} \over 2} = 2.5$$

C2 $$ \Rightarrow $$ $$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}{\sigma ^*}2{s^2}\sigma 2p_z^2\pi 2p_y^2$$ $$ \Rightarrow $$ Diamagnetic

Bond order = $${{8 - 4} \over 2} = 2$$

C2+ $$ \Rightarrow $$ $$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}{\sigma ^*}2{s^2}\sigma 2p_z^2\pi 2p_y^1$$ $$ \Rightarrow $$ Paramagnetic

Bond order = $${{7 - 4} \over 2} = 1.5$$

NO $$ \Rightarrow $$ $$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}{\sigma ^*}2{s^2}\sigma 2p_z^2\pi 2p_y^2{\pi ^*}2p_x^1$$ $$ \Rightarrow $$ Paramagnetic

Bond order = $${{10 - 5} \over 2} = 2.5$$

NO+ $$ \Rightarrow $$ $$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}{\sigma ^*}2{s^2}\sigma 2p_z^2\pi 2p_x^2\pi 2p_y^2$$ $$ \Rightarrow $$ Diamagnetic

Bond order = $${{10 - 4} \over 2} = 3$$

N2 $$ \Rightarrow $$ $$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}{\sigma ^*}2{s^2}\pi 2p_x^2\pi 2p_y^2\sigma 2p_z^2$$ $$ \Rightarrow $$ Paramagnetic

Bond order = $${{10 - 4} \over 2} = 3$$

N2+ $$ \Rightarrow $$ $$\sigma 1{s^2}{\sigma ^*}1{s^2}\sigma 2{s^2}{\sigma ^*}2{s^2}\pi 2p_x^2\pi 2p_y^2\sigma 2p_z^1$$ $$ \Rightarrow $$ Paramagnetic

Bond order = $${{9 - 4} \over 2} = 2.5$$
2
MCQ (Single Correct Answer)

NEET 2013 (Karnataka)

The outer orbitals of C in ethane molecule can be considered to be hybridized to give three equivalent sp2 orbitals. The total number of sigma $$\left( \sigma \right)$$ and pi $$\left( \pi \right)$$ bonds in ethane molecule is
A
3 sigma $$\left( \sigma \right)$$ and 2 pi $$\left( \pi \right)$$ bonds
B
4 sigma $$\left( \sigma \right)$$ and 1 pi $$\left( \pi \right)$$ bonds
C
5 sigma $$\left( \sigma \right)$$ and 1 pi $$\left( \pi \right)$$ bonds
D
1 sigma $$\left( \sigma \right)$$ and 2 pi $$\left( \pi \right)$$ bonds

Explanation

3
MCQ (Single Correct Answer)

NEET 2013 (Karnataka)

In which of the following pair both the species have sp3 hybridization ?
A
SiF4, BeH2
B
NF3, H2O
C
NF3, BF3
D
H2S, BF3

Explanation

NF3 and H2O are sp3-hybridisation
4
MCQ (Single Correct Answer)

NEET 2013

Which of the following is paramagnetic?
A
CN$$-$$
B
NO+
C
CO
D
O2$$-$$

Explanation

$$O_2^-$$ superoxide has one unpaired electron.

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