31.

Which one of the following oxides is reduced by water gas to obtain the metal during its extraction?

• NiO

• ZnO

• WO₃

• Fe₂O₃

0.16 g of an organic compound containing sulphur produces 0.233 g of BaSO₄. Percentage of sulphur in the compound is

• 20

• 80

• 50

• 10

The order of reactivity of phenol (I), nitrobenzene (II) and benzene (III) towards nitration is

• (III) > (I) > (II)

• (II) > (III) > (I)

• (I) > (III) > (II)

• (I) > (II) > (III)

The reagent used in the Wolff-Kishner reduction is

• H₂N-NH₂/ KOH

• H₂/ Ni

• Sn/ HCl

• LiAlH₄

The pK_a values of four carboxylic acids are 4.76, 4.19, 0.23 and 3.41 respectively. The pK_a value ofstrongest carboxylic acid among them is

• 4.19

• 3.41

• 0.23

• 4.76

Which one of the following is not a biopolymer?

• Cellulose

• Nylon-6

• Insulin

• DNA

Which one of the following statements is not correct?

• Except glycine all other naturally occurring α-amino acids are optically active.

• α-amino acids have maximum solubility at their isoelectric point.

• A tripeptide has two peptide bonds.

• α-amino acids exist as Zwitter ions.

Which one of the following is an artificial sweetening agent?

Which one of the following is true for an exothermic reaction A $\rightleftharpoons$ B, if E_f and E_b are the activation energies of forward and backward reactions respectively?

• E_f > E_b

• E_f = E_b

• E_f = -E_b

• E_f < E_b

Assertion (A) : Cyclohexane is the most stable cycloalkane.

Reason (R) : Cyclopropane and cyclobutane are less stable due to angle starin and torsional strain.

The correct answer is-

• Both (A) and (R) are true but (R) is not the correct explanation of (A).

• (A) is true but (R) is not true.

• (A) is not true but (R) is true.

• Both (A) and (R) are true and (R) is the correct explanation of (A).