Which of the following pairs contains species that are not isostructural?

1. ${\mathrm{IO}}_3^{-}\text{and\hspace{0.17em}}{\mathrm{XeO}}_3$

2. ${\mathrm{BH}}_4^{-}\text{and\hspace{0.17em}}{\mathrm{NH}}_4^{+}$

3. ${\mathrm{PF}}_6^{-}\text{and\hspace{0.17em}}{\mathrm{SF}}_6$

4. ${\mathrm{SiF}}_4\text{\hspace{0.17em}and\hspace{0.17em}}{\mathrm{SF}}_4$

The rate of a first-order reaction is 1.5 ×10^–2 mol L^–1 min^–1 at 0.5 M concentration of the reactant. The half-life of the reaction is:

The structure that represents the peptide chain is:

1.
2.
3.
4.

Which one among the given options, can be oxidized to produce a carbonyl compound?

1. o-Nitrophenol

2. Aniline

3. 2-Methyl-2-hydroxypropane

4. 2-Hydroxy propane 

In an octahedral structure, the pair of d orbitals involved in d²sp³ hybridization is:

1. ${\mathrm{d}}_{\mathrm{xz}},{\mathrm{d}}_{\mathrm{x}}^2-{\mathrm{y}}^2$

2. ${\mathrm{d}}_{\mathrm{z}}^2,{\mathrm{d}}_{\mathrm{xz}}$

3. ${\mathrm{d}}_{\mathrm{xy}},{\mathrm{d}}_{\mathrm{yz}}$

4. ${\mathrm{d}}_{\mathrm{x}}^2-{\mathrm{y}}^2,{\mathrm{d}}_{\mathrm{z}}^2$

The frequency of radiation emitted when the electron falls from n = 4 to n = 1 in a hydrogen atom will be:
(Given ionization energy of H = 2.18 × 10^–18 J atom ^–1 and h = 6.625 × 10^–34 Js):

1. 1.03 × 10¹⁵ s^–1

2. 3.08 × 10¹⁵ s^–1

3. 2.00 × 10¹⁵ s^–1

4. 1.54 × 10¹⁵ s^–1

Camphor is often used in molecular mass determination because:

1. It has a very high cryoscopic constant

2. It is volatile

3. It is a solvent for organic substances

4. It is readily available 

The number of chiral carbons in β–D–(+)– glucose is:

1. Six

2. Three

3. Four

4. Five 

The helical structure of a protein is stabilized by:

The compound that is least reactive towards nucleophilic substitution reaction is:

1. ${\mathrm{CH}}_2=\mathrm{CHCl}$

2. ${\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{Cl}$

3. ${\mathrm{CH}}_2={\mathrm{CHCH}}_2\mathrm{Cl}$

4. ${\left({\mathrm{CH}}_3\right)}_3\mathrm{C}-\mathrm{Cl}$