Class 11th

An alkyl halide C₅H₁₁Br (A) reacts with ethanolic KOH to give an alkene 'B', which reacts with Br₂ to give a compound 'C', which on dehydrobromination gives an alkyne 'D'. On treatment with sodium metal in liquid ammonia one mole of 'D' gives one mole of the sodium salt of 'D' and half a mole of hydrogen gas. Complete hydrogenation of 'D' yields a straight chain alkane. Identify A,B, C and D. Give the reactions invovled.

33. Which one is the correct unit for entropy?

(a) KJ mol                   

(b) JK mol

(c) JK mol^-1                     

(d) KJ mol^-1

32. Which of the following always has a negative value?

(a) Heat of reaction                           

(b) Heat of solution

(c) Heat of combustion                     

(d) Heat of formation

31. An isochoric and isobaric process takes place at constant

(a) Temperature and pressure respectively

(b) Pressure and concentration respectively

(c) Volume and pressure respectively

(d) Concentration and temperature respectively

30. Thermodynamics is applicable to

(a) Macroscopic system only                         

(b) Microsopic system only

(c) Homogeneous system only                     

(d) Heterogeneous system only

29. Which of the following statements is incorrect?

(a) Entropy is a measure of disorder or randomness.

(b) First law of thermodynamics does not guide us about the direction of chemical reactions

(c) Variables like p, V, T are called state variables or state functions.

(d) The state of the surroundings can always be completely specified.

28. Reaction spontaneous at all temperatures when:

(a) Δ_rH^? is negative, Δ_rS^? positive, Δ_rG^? is negative.

(b) Δ_rH^? is positive, Δ_rS^? positive, Δ_rG^? is negative.

(c) Δ_rH^? is negative, Δ_rS^? positive, Δ_rG^? is positive.

(d) Δ_rH^? is positive, Δ_rS^? positive, Δ_rG^? is positive.

27. Assertion: It requires less heat to vaporise 1 mol of acetone than it does to vaporize 1 mol of water.

Reason: For an organic liquid, such as acetone, the intermolecular dipole-dipole interactions are significantly weaker.

26. Assertion: When temperature of a crystalline solid is increased, the degree of randomness of its constituents increases.

Reason:The entropy of any pure crystalline substance approaches zero as the temperature approaches absolute zero.

25. Assertion: Entropy decreases when a liquid crystallizes into solid.

Reason: Molecules tend to be in a less ordered state.