Chemical Bonding and Molecular Structure Chapter-Wise Test 13

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which of the following molecules is diamagnetic?

\( \ce{Li2} \) has the configuration \( (\sigma 1s)^2 (\sigma^* 1s)^2 (\sigma 2s)^2 \), with all electrons paired, making it diamagnetic.

\( \ce{O2} \)
\( \ce{B2} \)
\( \ce{Li2} \)
\( \ce{NO} \)
3

Which molecule has a bond angle of exactly 120° due to \( sp^2 \) hybridization and no lone pairs?

In \( \ce{BH3} \), boron is \( sp^2 \) hybridized with 3 bonding pairs and no lone pairs, forming a trigonal planar shape with 120° bond angles.

\( \ce{SO2} \)
\( \ce{NH3} \)
\( \ce{BH3} \)
\( \ce{H2O} \)
3

The bond order of \( \ce{H2^+} \) ion according to molecular orbital theory is:

For \( \ce{H2^+} \): \( (\sigma 1s)^1 \). Bonding = 1, antibonding = 0. Bond order = \( \frac{1 - 0}{2} = 0.5 \).

0.5
1
1.5
2
1

Which molecule has a tetrahedral electron pair geometry but a trigonal pyramidal molecular shape?

In \( \ce{NF3} \), nitrogen has four electron pairs (three bonding, one lone), giving tetrahedral electron geometry, but the lone pair results in a trigonal pyramidal shape.

\( \ce{NF3} \)
\( \ce{BF3} \)
\( \ce{CH4} \)
\( \ce{CO2} \)
1

Which molecule has a bond angle of exactly 90° in its octahedral electron geometry?

In \( \ce{SF6} \), sulfur is \( sp^3d^2 \) hybridized with 6 bonding pairs, forming an octahedral shape with 90° bond angles.

\( \ce{PF5} \)
\( \ce{ClF3} \)
\( \ce{XeF4} \)
\( \ce{SF6} \)
4

The number of pi bonds in \( \ce{C5H6} \) (cyclopentadiene, \( \ce{C5H6} \) with two double bonds) is:

In cyclopentadiene (\( \ce{CH=CH-CH=CH-CH2} \) in a ring), there are 2 double bonds, each with 1 pi bond, totaling 2 pi bonds, plus 13 sigma bonds.

1
3
4
2
4

Which molecule exhibits paramagnetism due to unpaired electrons?

For \( \ce{B2} \): \( (\sigma 1s)^2 (\sigma^* 1s)^2 (\sigma 2s)^2 (\sigma^* 2s)^2 (\pi 2p_x)^1 (\pi 2p_y)^1 \), with two unpaired electrons, making it paramagnetic.

\( \ce{N2} \)
\( \ce{F2} \)
\( \ce{B2} \)
\( \ce{H2} \)
3

The number of sigma bonds in \( \ce{C3H8} \) (propane) is:

In \( \ce{C3H8} \), there are 2 \( \ce{C-C} \) sigma bonds and 8 \( \ce{C-H} \) sigma bonds, totaling 10 sigma bonds.

8
9
10
11
3

Which molecule has a trigonal bipyramidal shape?

In \( \ce{PF5} \), phosphorus is \( sp^3d \) hybridized with five bonding pairs, resulting in a trigonal bipyramidal shape.

\( \ce{SF6} \)
\( \ce{PF5} \)
\( \ce{BF3} \)
\( \ce{NH3} \)
2

Which molecule has a bond order of 2 and is diamagnetic?

For \( \ce{C2} \): \( (\sigma 1s)^2 (\sigma^* 1s)^2 (\sigma 2s)^2 (\sigma^* 2s)^2 (\pi 2p_x)^2 (\pi 2p_y)^2 \). Bonding = 8, antibonding = 4. Bond order = \( \frac{8 - 4}{2} = 2 \), with all electrons paired (diamagnetic).

\( \ce{O2} \)
\( \ce{B2} \)
\( \ce{C2} \)
\( \ce{NO} \)
3

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