H₂S gas when passed through a solution of cations containing HCl precipitates the cations of the second group in qualitative analysis but not those belonging to the fourth group. It is because: 
 

The addition of HCl does not suppress the ionization of:

In which of the following will the solubility of AgCl be the minimum?

In an acidic Buffer solution (CH₃COOH + CH₃COONa), the species mainly present in the solution are:

(Ignore negligible amount)

1. CH₃COOH, CH₃COO^-, CH₃COONa, H⁺

2. CH₃COO^-, Na⁺, CH₃COOH

3. CH₃COONa, CH₃COO-, H⁺

4. CH₃COO^-, Na⁺, H⁺, CH₃COONa

When NH₄Cl is added in NH₄OH solution, then pH of the solution

1. Increases

2. Decreases

3. Remains unchanged

4. Firstly decreases and more than decreases

Consider the nitration of benzene using mixed conc. H₂SO₄ and HNO₃.
If a large amount of KHSO₄ is added to the mixture, the rate of nitration will be:

On adding NH₄CI to an NH₄OH solution, the pH of the solution will

Out of ${\mathrm{Ca}}^{2+},\hspace{0.17em}{\mathrm{Al}}^{3+},\hspace{0.17em}{\mathrm{Cr}}^{3+},<mspace\; width="1em"></mspace>{\mathrm{Mg}}^{2+},<mspace\; width="1em"></mspace>\mathrm{and}<mspace\; width="1em"></mspace>{\mathrm{Zn}}^{2+},$ 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. ${\mathrm{Al}}^{3+},<mspace\; width="1em"></mspace>{\mathrm{Cr}}^{3+}$

3. ${\mathrm{Bi}}^{3+},<mspace\; width="1em"></mspace>{\mathrm{Mg}}^{2+}$

4. ${\mathrm{Mg}}^{2+},<mspace\; width="1em"></mspace>{\mathrm{Zn}}^{2+}$

What happens when NH₄Cl is added to an aqueous solution of NH₄OH?

1. Concentration of $\left[{\mathrm{OH}}^{-}\right]$ ions decreases.

2. Concentration of $\left[{\mathrm{OH}}^{-}\right]$ ions increases.

3. Concentration of $\left[{\mathrm{NH}}_4^{+}\right]$ ions as well as concentration $\left[{\mathrm{OH}}^{-}\right]$ ions increase.

4. Concentration of $\left[{\mathrm{NH}}_4^{+}\right]$ ions decreases.