Which of the following combinations can be used to prepare a buffer solution?

I. Sodium acetate and acetic acid in water

II. Sodium acetate and hydrochloric acid in water

III. Ammonia and ammonium chloride in water

IV. Ammonia and sodium hydroxide in water.

1. I, III, IV

2. III, IV

3. I, II, IV

4. I,  III

The basic buffer solution among the following is: 

1. ${\mathrm{NH}}_4\mathrm{Cl}+{\mathrm{NH}}_4\mathrm{OH}$

2. $\mathrm{NaCl}+\mathrm{NaOH}$

3. ${\mathrm{NH}}_4\mathrm{Cl}+{\mathrm{CH}}_3\mathrm{COOH}$

4. ${\mathrm{CH}}_3\mathrm{COONa}+{\mathrm{CH}}_3\mathrm{COOH}$

Conjugate base of hydrazoic acid is: 

1. \({HN_3}^-\)${}_{}^{}$

2. \(N_2^-\)   ${\mathrm{}}_{}^{}$

3. \(N_3^-\) 
4. \({N^3}^-\)

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:

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