NEET Practice Questions (MCQs) with Answers & Solutions

(c)

To precipitate soap from its saturated solution on addition of salt is called salting out the action of soap.

                        RCOONa $\rightleftharpoons$RCOO^- + Na⁺

                          K_sp = [RCOO^-][Na⁺]

(a) H₃PO₂ is monobasic acid and thus, it forms only one normal salt.

(b) For equilibrium,

(i)  N₂ (g) + 3H₂ (g) $\rightleftharpoons$ 2NH₃ (g),

                  K₁ = [NH₃]²/[N₂][H₂]³                           ...(i)

(ii)  N₂(g) + O₂(g) $\rightleftharpoons$ 2NO (g),

                 K₂ = [NO]²/[N₂][O₂]                             .....(ii)

(iii) H₂(g) + $\frac{1}{2}$O₂(g) $\rightleftharpoons$ H₂O (g),

                 K₃ = [H₂O]/[H₂][O₂]^1/2                        ......(iii)

 For the reaction,

    2NH₃ (g) + 5/2 O₂ (g) $\rightleftharpoons$ 2NO (g) + 3H₂O (g) 

                 K = [NO]²[H₂O]³/[NH₃]²[O₂]^5/2            ....(iv)

    Equation (iii) multiplied by 3

           3H₂ + 3/2 O₂ (g) $\rightleftharpoons$ 3H₂O

   then,      $K_{\mathit{3}}^{\mathit{3}}$ = [H₂O]³/[H₂]³[O₂]^3/2

 From eqs. (i), (ii) and (v) 

           K = (K₂ x $K_{\mathit{3}}^{\mathit{3}}$)/K₁

(b) Higher pK_a (-logK_a) means lower K_a for acid.

(c) Fe³⁺ + 3H₂O $\to$Fe(OH)₃ + 3H⁺

(d) It involves gain and loss of electron pair (Lewis concept).

(a) K_p = (ⁿCl₂ x ⁿPCl₃)/ⁿPCl₅ x [p/$\Sigma n$]¹ = 2x2/2 x[3/6]¹ = 1 atm

(d) K_a for H₂S = [H⁺][HS^-]/H₂S ;

An increase in [H⁺] will show a decrease in [HS^-] to maintain constant K_a value.

(c) NaCl (s) $\rightleftharpoons$Na⁺ (aq) + Cl^- (aq);  HCl$\to$ H⁺ + Cl^-

The increase in [Cl^-] brings in an increase in [ Na⁺][Cl^-] which will lead for backward reaction because,

        K_spNaCl = [Na⁺][Cl^-]

(d) e.g., CH₃COONa;

              CH₃COO^- + H₂O $\rightleftharpoons$ CH₃COOH + OH^-