31.

For the reaction,

A (g) + 2B (g) → 2C (g) + 3D (g)

the change of enthalpy at 27°C is 19 kcal. The value of $∆$E is

• 21.2 kcal

• 17.8 kcal

• 18.4 kcal

• 20.6 kcal

Glucose is added to 1 L water to sch an extent that $∆{\mathrm{T}}_{\mathrm{f}}/ {\mathrm{K}}_{\mathrm{f}}$becomes equal to 10^-3, the weight of glucose (C₆H₁₂O₆ ) added is

• 180 gm

• 18 gm

• 1.8 gm

• 0.18 gm

Manganese salt + PbO₂ + conc. HNO₃ → the solution acquires purple colour. The colour is due to

• Mn(NO₃)₂

• Pb(NO₃)₂

• HMnO₄

• MnO

One faraday of current was passed through the electrolytic cells placed in series containing solution of Ag⁺, Ni²⁺ and Cr³⁺ respectively. The ratio of amounts of Ag, Ni and Cr deposited will be

(atomic weigth of Ag = 108, Ni = 59 and Cr = 52)

• 108, 29.5, 17.4

• 17.4, 29.5, 108

• 1, 2, 3

• 108, 59, 52

In the extraction of copper, metal is formed is the Bessemer converter due to reaction

• 2Cu₂S + 2Cu₂O  → 6Cu + SO₂

• 2Cu₂O → 4Cu + O₂

• Cu₂S → 2Cu + S

• Fe + Cu₂O → 2Cu + FeO

Which are of the following is a false statement?

• Cell fluid is an example of sol

• Butter is an example of gel

• Hair cream is an example of emulsion

• Cheese is an example of foam

50 g of saturated aqueous solution of potassium chloride at 30°C is evaporated to dryness, when 13.2 gm of dry KCl was obtained. The solubility of KCl in water at 30°C is

• 35.87 g

• 25.62 g

• 28.97 g

• 27.81 g

Zinc is used to protect iron from corrosion because

• E_red of An < E_red of iron

• E_oxidation of Zn < E_oxidation of iron

• E_oxidation of Zn = E_oxidation of iron

• Zinc is cheaper than iron

At room temperature, the reaction between NO and O₂ to give NO₂ is fast while that of between CO and O₂ is slow. It is because

• the intrinsic energy of the reaction 2NO + O₂ $\rightleftharpoons$ 2NO₂ is less

• CO is smaller in size than that of NO

• CO is poisonous

• the activation energy for the reaction 2 NO + O₂ $\rightleftharpoons$ 2NO₂ is less

A radioactive isotope having a half-life of 3 days was received after 12 days. It was found that there were 3 g of the isotope in the container. Find the initial weight of the isotope, when it was packed (antilog 1.203 = 16)

• 12 gm

• 24 gm

• 36 gm

• 48 gm