21.

Dihedral angle between two methyl groups of n-butane in the gauche and anti forms are

• 60°, 0°

• 0°, 60°

• 60$°$, 180°

• 180°, 60°

The vapour pressure of 100g water reduces from 3000 Nm^-2 to 2985 Nm^-2 when 5g of substance 'X' is dissolved in it. Substance 'X' is

• methanol

• glucose

• carbon dioxide

• cannot predict

The complex ion which has no d-electrons in the central metal atom is

• [MnO₄]^-

• [Co(NH₃)₆]³⁺

• [Fe(CN)₆]^3-

• [Cr(H₂O)₆]³⁺

White P reacts with caustic soda, the products are PH₃ and NaH₂PO₂. This reaction is an example of

• hydrolysis

• reduction

• disproportionation

• neutralisation

The solubility of saturated solution of Ag₂CrO₄ is s mol L^-1. What is its solubility product?

• 4s³

• s³

• 2s³

• 16s²

For a reaction, A+ B $\to$ Product, the rate is given by,

r = k[A]^1/2[B]²

What is the order of the reaction?

• 0.5

• 2

• 2.5

• 1

How long it will take to deposit 1.0 g of chromium when a current of 1.25 A flows through a solution of chromium (III) sulphate ? (Molar mass of Cr = 52)

• 1.24 min

• 1.24 h

• 1.24 s

• None of these

If a be the edge length of the unit cell and r be the radius of an atom then for fee arrangement, the correct relation is

• 4a = $\sqrt{3}$r

• 4r = $\sqrt{3}$a

• 4r = $\sqrt{2}$a

• 4r = $\frac{\mathrm{a}}{\sqrt{2}}$

The number of phase in a colloidal system is

• 1

• 2

• 3

• 4

A solid AB has the NaCl structure. If radius of cation A⁺ is 120 pm, the maximum possible value of the radius of the anion B^- is

• 240 pm

• 60 pm

• 49.6 pm

• 290 pm