Which of the following are Lewis acids?

(i) ${\mathrm{BF}}_3$

(ii) ${\mathrm{H}}_2\mathrm{O}$

(iii) ${\mathrm{HSO}}_4^{-}$

(iv) ${\mathrm{SO}}_3$

1. (i) and (iii)

2. (i) and (ii)

3. (i) and (iv)

4. (iii) and (iv)

Out of ${\mathrm{Ca}}^{2+},\hspace{0.17em}{\mathrm{Al}}^{3+},\hspace{0.17em}{\mathrm{Cr}}^{3+}, {\mathrm{Mg}}^{2+}, \mathrm{and} {\mathrm{Zn}}^{2+},$ the reagents ${\mathrm{NH}}_4\mathrm{Cl}$ and aqueous ${\mathrm{NH}}_3$ will precipitate

1. ${\mathrm{Ca}}^{2+},\hspace{0.17em}{\mathrm{Al}}^{3+}$

2. ${\mathrm{Al}}^{3+}, {\mathrm{Cr}}^{3+}$

3. ${\mathrm{Bi}}^{3+}, {\mathrm{Mg}}^{2+}$

4. ${\mathrm{Mg}}^{2+}, {\mathrm{Zn}}^{2+}$

Which among the following is the least soluble?

1. $\mathrm{MnS} ({\mathrm{K}}_{\mathrm{sp}}=7\times {10}^{-16})$

2. $\mathrm{FeS} ({\mathrm{K}}_{\mathrm{sp}}=4\times {10}^{-19})$

3. $\mathrm{PtS} ({\mathrm{K}}_{\mathrm{sp}}=8\times {10}^{-73})$

4. $\mathrm{NiS} ({\mathrm{K}}_{\mathrm{sp}}=3\times {10}^{-12})$

The dissociation constant of a substituted benzoic acid at $25°\mathrm{C}$ is $1\times {10}^{-4}.$ The pH of a 0.01 m solution of its sodium salt of benzoic acid is

1. 6

2. 7

3. 8

4. 9

Which one of the following is true for any diprotic acid, ${\mathrm{H}}_2\mathrm{X}$?

1. ${\mathrm{Ka}}_1={\mathrm{Ka}}_2$

2. ${\mathrm{Ka}}_2>{\mathrm{Ka}}_1$

3. ${\mathrm{Ka}}_1>{\mathrm{Ka}}_2$

4. ${\mathrm{Ka}}_2=1/{\mathrm{Ka}}_1$

For sparingly soulble salt ${\mathrm{A}}_{\mathrm{p}}{\mathrm{B}}_{\mathrm{q}}$, the relationship of its solubility product $\left({\mathrm{L}}_{\mathrm{s}}\right)$ with its solubility (s) is

1. ${\mathrm{L}}_{\mathrm{s}}={\mathrm{s}}^{\mathrm{p}+\mathrm{q}}.{\mathrm{p}}^p.{\mathrm{q}}^{\mathrm{q}}$

2. ${\mathrm{L}}_{\mathrm{s}}={\mathrm{s}}^{\mathrm{p}+\mathrm{q}}.{\mathrm{p}}^{\mathrm{q}}.{\mathrm{q}}^{\mathrm{q}}$

3. ${\mathrm{L}}_{\mathrm{s}}={\mathrm{s}}^{\mathrm{pq}}{\mathrm{p}}^{\mathrm{q}}{\mathrm{q}}^{\mathrm{q}}$

4. ${\mathrm{L}}_{\mathrm{s}}={\mathrm{s}}^{\mathrm{pq}}.{\left(\mathrm{pq}\right)}^{\mathrm{p}+\mathrm{q}}$

pKa values of three acids A, B and C are 4.3, 3.3 and 5.5 respectively. Which of the following represents the correct order of acid strength?

1. A>B>C

2. C>A>B

3. B>A>C

4. C>B>A

Which of the following statements is correct?

I. The pH of $1.0\times {10}^{-8 }\mathrm{M}$ solution of HCl is 8

II. The conjugate base of ${\mathrm{H}}_2{\mathrm{PO}}_4^{-}$ is ${\mathrm{HPO}}_4^{2-}$

III. Autoprotolysis constant of water increases with temperature

IV. When a solution of a weak monoprotic acid is titrated against a strong base at half neutralization point, pH = (1/2) pKa.

1. II, III

2. I, II, III

3. III, IV

4. II, III, IV

The solubility of ${\mathrm{A}}_2{\mathrm{X}}_3$ is y mol dm^-3. Its solubility product is

1. $6 {\mathrm{y}}^4$

2. $64 {\mathrm{y}}^4$

3. $36 {\mathrm{y}}^5$

4. $108 {\mathrm{y}}^5$

If ${\mathrm{pK}}_{\mathrm{b}}$ for fluoride ion at $25°\mathrm{C}$ is 10.83, the ionization constant of hydrofluoric acid at this temperature is

1. $1.74\times {10}^{-5}$

2. $3.52\times {10}^{-3}$

3. $6.75\times {10}^{-4}$

4. $5.38\times {10}^{-2}$