VITEEE 2017 :: Chemistry :: General questions

• Chemistry - General questions

Iron crystallizes in several modifications. At about 911°C, the bcc ' α ' form undergoes a transition to fcc 'γ ' form. If the distance between the two nearest neighbours is the same in the two forms at the transition temperature, the ratio of the density of iron in fcc form (ρ₂) to that of iron of bcc form (ρ₁ ) at the transition temperature

Answer:

Explanation:

 In α - form distance between nearest neighbour atom is $\frac{\sqrt{3}a_{1}}{2}$

In γ form distance between nearest neighbour atom is $\frac{a_{2}}{\sqrt{2}}$

.'. $\frac{\sqrt{3}a_{1}}{2}$ = $\frac{a_{2}}{\sqrt{2}}$  (given)

or $\frac{a_{2}}{a_{1}}= \sqrt{\frac{3}{2}}$

$\frac{\rho_{1}}{\rho_{2}}= \frac{z_{1}}{z_{2}}\left(\frac{a_{2}}{a_{}}\right)^{3}$

= $\frac{1}{2}\left(\sqrt{\frac{3}{2}}\right)^{3}$ = 0.918

The standard reduction potential for Cu²⁺ /Cu is + 0.34. Calculate the reduction potential at pH = 14 for the above couple. (K_sp Cu(OH)₂ = 1×10^-19

Answer:

Explanation:

When pH = 14 [H]⁺ = 10^-14 

and [OH^-] = 1M

K_sp = [Cu²⁺] [OH^-]² = 10^-19

.'. [Cu²⁺] = $\frac{10^{-19}}{[OH^{-]^{2}}}$ = 10^-19

The half cell reaction

Cu²⁺ + 2e^- → Cu

E = E⁰ - $\frac{0.059}{2}\log_{}{}\frac{1}{[Cu^{2+}]}$

= 0.34 - $\frac{0.059}{2}\log_{}{}\frac{1}{10^{-19}}$ = -0.22V

The number of aldol reaction(s) that occurs in the given transformation is :

Answer:

Explanation:

The emf of a particular voltaic cell with the cell reaction $Hg_{2}^{2}+ +H_{2} \rightleftharpoons 2Hg+H^{+}$ is 0.65 V. The maximum electrical work of this cell when 0.5 g of H₂ is consumed.

Answer:

Explanation:

W_max = -n.FE

Wmax = -2 x 96500 x 0.65 = -1.25 x 10⁵J

0.5g H₂ = 0.25 mole.

Hence, W_max = 1.25 x 10⁵ x 0.25 = -3.12 x 10⁴ J

A substance C₄H₁₀O yields on oxidation a compound, C₄H₈O which gives an oxime and a positive iodoform test. The original substance on treatment with conc. H₂SO₄ gives C₄H₈. The structure of the compound is

Answer:

Explanation:

Thus $C_{4}H_{8}O$ should be $CH_{3}COCH_{2}CH_{3}$, hence C₄H₁₀O should be $CH_{3}CHOHCH_{2}CH_{3}$

• Chemistry - General questions