Which of the following is least likely to behave as Lewis base?

1. $N{H}_3$

2. $B{F}_3$

3. $O{H}^{-}$

4. $H_{2}O$

In DNA, the complementary bases are:

1. Adenine and thymine; guanine and cytosine

2.  Adenine and thymine; guanine and uracil

3.  Adenine and guanine ; thymine and cytosine

4. Uracil and adenine, cytosine and guanine

Which one of the following does not undergo an iodoform reaction?

1. Secondary butyl alcohol

2. So-propyl alcohol

3. Diethyl ketone

4. Ethyl alcohol

Percentage of free space in a body centre cubic unit cell is:

1. 30%

2. 32%

3. 34%

4. 28%

For the reaction, N2 (g) +O2 (g) 2NO (g), the equilibrium constant is k1. The equilibrium constant is K2 for the reaction, 2NO (g) +O2 (g) 2NO2 (g). What is k for the reaction, NO2 (g) N2?

1. $1/\left(4K_1{K}_2\right)$

2. $[1/K_1{K}_2{]}^{1/2}$

3. $11\left(K_1{K}_2\right)$

4. $11\left(2K_1{K}_2\right)$

Acidified K₂Cr₂O₇ solution turns green when Na₂SO₃ is added to it. This is due to the formation of:

1. $Cr{O}^{-}$

2. $C{r}_2{\left(S{0}_3\right)}_3$

3. $CrS{O}_4$

4. $C{r}_2{\left(S{O}_4\right)}_3$

Among the following the least thermally stable is:

1. $K_{2}C{O}_3$

2. $N{a}_{2}C{O}_3$

3. $BaC{O}_3$

4. $L{i}_{2}C{O}_3$

Which one of the following is 'd' block element?

1. Gd

2. Hs

3. Es

4. Cs

The angular shape of ozone molecule (0₃) consists of:

1. 1 sigma and 2 pi bonds

2. 2 sigma and 2 pi bonds

3. 1 sigma and 1 pi bonds

4. 2 sigma and 1 pi bonds