If Ksp of Al(OH)₃ is $1.0\times {10}^{-15} \mathrm{M}.$ Find at what pH does $1.0\times {10}^{-3} \mathrm{M}$ Al³⁺ precipitate on the addition of buffer of NH₄Cl and NH₄OH solution.

1. 10

2. 10.5

3. 11

4. 12

The solubility of CaF₂ in water at 298 K is $1.7\times {10}^{-3}$ gm per 100 cm³. The solubility product of CaF₂ at 298 K is

1. $4.14\times {10}^{-11}$

2. $4.14\times {10}^{11}$

3. $4.14\times {10}^{-6}$

4. $4.14\times {10}^6$

A solution of monoprotic weak acid has acidity constant K_a the minimum intial concentration 'c' in terms of K_a, such that the concentration of the undissociated acid can be equated to 'c' within a 10% limit of error, would be

1. 70 K_a

2. 90 K_a

3. 50 K_a

4. 30 K_a

The solubility product of PbI₂ is $7.47\times {10}^{-9}$ at $15°\mathrm{C}$ and $1.39\times {10}^8$ at $25°\mathrm{C}$. The molar heat of solution of PbI₂ is (use log 1.86=0.2695)

1. 44.29 kJ/mol

2. 46.25 kJ/mol

3. 29.37 kJ/mol

4. 21.15 kJ/mol

Which of the following compounds is in the correct sequence in terms of relative basic strength?

1. ${\mathrm{C}}_2{\mathrm{H}}_5{\mathrm{O}}^{-}>\mathrm{CH}\equiv {\mathrm{C}}^{-}>{\mathrm{OH}}^{-}$

2. $\mathrm{CH}\equiv {\mathrm{C}}^{-}{>}^{-}\mathrm{OH}>{\mathrm{C}}_2{\mathrm{H}}_5{\mathrm{O}}^{-}$

3. $\mathrm{CH}\equiv {\mathrm{C}}^{-}>{\mathrm{C}}_2{\mathrm{H}}_5{\mathrm{O}}^{-}>{\mathrm{OH}}^{-}$

4. ${\mathrm{C}}_2{\mathrm{H}}_5{\mathrm{O}}^{-}>{\mathrm{OH}}^{-}>\mathrm{CH}\equiv {\mathrm{C}}^{-}$

The concentration of CH₃COOH that will have the same [H⁺] as obtained from 10^-2 M HCOOH, is-

$\left(\mathrm{Ka}\right({\mathrm{CH}}_3\mathrm{COOH})={10}^{-5},$ $\mathrm{Ka}\left(\mathrm{HCOOH}\right)={10}^{-4})$

1. 10 M

2. 5 M

3. 10^-1 M

4. 6 M

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.

500 ml of 0.2 M HCl is mixed with 500 ml of 0.2 M CH₃COOH. 25 ml of the mixture is titrated with 0.1 M NaOH solution. By how many units does the pH change from the start to the stage when HCl is just completely neutralized. K_a for acetic acid$=2.0\times {10}^{-5}$.

1. 3.7

2. 4.4

3. 2.0

4. 3.0

When 60 ml of 0.1 M $\mathrm{Ca}{\left({\mathrm{NO}}_3\right)}_2$ is mixed with 40 ml of 0.125 M ${\mathrm{Na}}_2{\mathrm{CO}}_3$, ${\mathrm{CaCO}}_3$ precipitates. If K_sp of ${\mathrm{CaCO}}_3$ is $5\times {10}^{-9}$, then $\left[{\mathrm{CO}}_3^{2-}\right]$ in the resulting solution is

1. $5\times {10}^{-8} \mathrm{M}$

2. $5\times {10}^{-9} \mathrm{M}$

3. $5\times {10}^{-6} \mathrm{M}$

4. $5\times {10}^{-7} \mathrm{M}$

100 ml of 0.3 M NH₄OH is mixed with 100 ml of 0.2 M NaOH. K_b NH₄OH is $1.8\times {10}^{-5}$. The degree of dissociation of NH₄OH is

1. $1.02\times {10}^{-2}$

2. $1.8\times {10}^{-5}$

3. $1.8\times {10}^{-4}$

4. $1.02\times {10}^{-4}$