Factors Affecting Alpha

Q. At ${80}^{\circ }C$, distilled water has hydronium ion $\left(H_3{O}^{+}\right)$ concentration equal to $1\times {10}^{-6}mol/L$. The value of $K_w$ at this temperature would be:

1. $1\times {10}^{-6}$
2. $1\times {10}^{-12}$
3. $1\times {10}^{-9}$
4. $1\times {10}^{-14}$

Q. How much sodium formate $(HCOONa,68.0069gmo{l}^{-1})$ is to be added to 400 mL of 1.00 M formic acid for a pH=3.50 buffer. Given $K_a=1.77\times {10}^{-4}$
$log1.77=0.248\text{and log}0.56=-2.52$

1. 20.25 g
2. 15.23 g
3. 30.34 g
4. 5.50 g

Q. Calculate $\left[H^{+}\right]$ of solution obtained by mixing equal volume of 0.02 M $HN{O}_2$ ( a weak acid) and 0.2 M $C{H}_{3}COOH$ solution.
Given that:
$K_{a_1}\left(HN{O}_2\right)=2\times {10}^{-4}$
$K_{a_2}\left(C{H}_{3}COOH\right)=2\times {10}^{-5}$
Where , $K_{a_1}and{K}_{a_2}$ are the dissociation constants of $HN{O}_{2}andC{H}_{3}COOH$ respectively.

1. $2\times {10}^{-3}M$
2. $4\times {10}^{-4}M$
3. $6\times {10}^{-3}M$
4. $8\times {10}^{-4}M$

Q. The initial rate of hydrolysis of methyl acetate (1M) by a weak acid (HA, 1M) is 1/100th of that of a strong acid (HX, 1M), at ${25}^{o}C.$ The $K_a$ of HA is

1. $1\times {10}^{-4}$
2. $1\times {10}^{-6}$
3. $1\times {10}^{-5}$
4. $1\times {10}^{-3}$

Q. Which of the following statements is/are correct about the ionic product of water?

1. At 298K , Equilibrium constant of water < ionic product of water
   i.e. $K_c<K_w$
2. $K_w$ at 373 K $>K_w$ at 298 K
3. Ionic product of water at ${25}^{\circ }C$ is ${10}^{-14}$
4. None of the above.

Q. The $\left[H^{+}\right]$ of the resulting solution that is 0.01 M in acetic acid $(K_a=1.8\times {10}^{-5}M)$ and 0.01 M in benzoic acid. $(K_a=6.3\times {10}^{-5}M)$ will be:

1. $4\times {10}^{-4}M$
2. $16\times {10}^{-4}M$
3. $81\times {10}^{-4}M$
4. $9\times {10}^{-4}M$

Q. For the gaseous reactions:
$A\left(g\right)\rightleftharpoons 3B\left(g\right):K_{P_1}andP\left(g\right)\rightleftharpoons 2Q\left(g\right)+R\left(g\right);K_{P_2}$
Occuring in two different vessels at the same temperature, the degree of dissociation of A and P are same when the total equilibrium pressure of gases in both vessels are same. If $K_{P_1}:K_{P_2}$ is $X:4,$ then value of "X" is

Q. If one litre of water contains ${10}^{-5}$ moles of $H^{+}$ ions at a certain temperature. Calculate the degree of ionization of water.

1. $18\times {10}^{-9}$
2. $3.6\times {10}^{-6}$
3. $1.8\times {10}^{-10}$
4. $1.8\times {10}^{-7}$

Q. At ${25}^{o}C,$ the dissociation constant $\left(K_a\right)$of a weak monoprotic acid, $HA$ is numerically equal to the dissociation constant $\left(K_b\right)$ of its conjugate base, $A^{-}.$ Which of the following statements (s) is/are correct?

1. The dissociation constant of the acid, HA, is ${10}^{-7}$
   
2. The pH of $0.1M$ aqueous solution of the acid, $HA$, is $4.0$
   
3. The pH of $0.1M$ aqueous solution of the conjugate base $\left(A^{-}\right)$ is $10.0$
   
4. The pH of an aqueous solution containing $0.1MHA$ and $0.01MHCl$ is $2.0$

Q. $0.02M$ solution of $H_{2}A$ has $pH=4$. If $K_{a_1}$ for the acid is $5\times {10}^{-7}M$, the concentration of $H{A}^{-}$ ion in the solution would be :

1. $2\times {10}^{-7}M$
2. $1\times {10}^{-6}M$
3. $3\times {10}^{-5}M$
4. $1\times {10}^{-4}M$

Q. A buffer solution that has a pH of $4.72$ is prepared by mixing of $1\text{M NaOH}$ and $1M\text{HCN}$. What is the ratio of volumes of the acid to the base? $(p{K}_b{\text{of CN}}^{-}=9.28)$

1. 1 : 1
2. 1 : 2
3. 2 : 1
4. 3 : 1

Q. Consider a solution of two weak acids $W{A}_1$ and $W{A}_2$.
Which of the following statement(s) is/are correct?

1. These two acids will dissociate less than in their individual solutions of the same concentration.
2. Common ion effect is not observed in case of mixture of two weak acids.
3. These two acids will dissociate more than in their individual solutions of the same concentration.
4. Common ion effect is observed in case of a mixture of two weak acids.

Q. What is the percentage degree of dissociation of $0.05MN{H}_{4}OH$ at $25{}^{o}C$ solution having $pH=10$ ?

1. $2.0$
2. $0.2$
3. $0.002$
4. $0.02$

Q. At ${25}^{o}C,$ the dissociation constant $\left(K_a\right)$of a weak monoprotic acid, $HA$ is numerically equal to the dissociation constant $\left(K_b\right)$ of its conjugate base, $A^{-}.$ Which of the following statements (s) is/are correct?

1. The dissociation constant of the acid, HA, is ${10}^{-7}$
   
2. The pH of $0.1M$ aqueous solution of the acid, $HA$, is $4.0$
   
3. The pH of $0.1M$ aqueous solution of the conjugate base $\left(A^{-}\right)$ is $10.0$
   
4. The pH of an aqueous solution containing $0.1MHA$ and $0.01MHCl$ is $2.0$

Q. The first and second dissociation constant of an acid $H_{2}A$ are $1.0\times {10}^{-5}$ and $5.0\times {10}^{-10}$ respectively. The overall dissociation constant of the acid will be:

1. $5.0\times {10}^{-5}$
2. $5.0\times {10}^{15}$
3. $5.0\times {10}^{-15}$
4. $0.2\times {10}^5$

Q. Find the dissociation constant $K_a$ of a weak monobasic acid which is 3.5% dissociated in a $\frac{M}{10}$ solution at ${25}^{\circ }C$

1. $0.5\times {10}^{-3}$
2. $2.62\times {10}^{-6}$
3. $4.2\times {10}^{-6}$
4. $1.27\times {10}^{-4}$

Q. For a given aqueous solution at ${25}^{o}C$ which of the following is correct regarding the nature of solution:

1. Acidic if $\left[H^{+}\right]<\sqrt{K_w}$
2. Alkaline if $\left[H^{+}\right]<\sqrt{K_w}$
3. Acidic if $\left[H^{+}\right]>\sqrt{K_w}$
4. Neutral if $\left[H^{+}\right]=\sqrt{K_w}$

Q. Which of the following relation is correct regarding $pH$ of salt of amphiprotic ion, $H_{2}P{O}_4^{-}$:
Given: $K_{a_1}$ is first acid dissociation constant of $H_{3}P{O}_4$ and $K_{a_2}$ is second acid dissociation constant of $H_{3}P{O}_4$.

1. $pH=\frac{p{K}_{a_1}}{2\times p{K}_{a_2}}$
2. $pH=\frac{1}{2}[p{K}_{a_1}\times p{K}_{a_2}]$
3. $pH=\frac{1}{2}[p{K}_{a_1}-p{K}_{a_2}]$
4. $pH=\frac{1}{2}[p{K}_{a_1}+p{K}_{a_2}]$

Q. Consider an aqueous solution containing $0.001M{H}_{2}S$ and $0.25MHCl$. If the equilibrium constants for the formation $H{S}^{-}$ from $H_{2}S$ is $1.0\times {10}^{-7}$ and that of $S^{2-}$ from $H{S}^{-}$ is $1.2\times {10}^{-13}$. Then the concentration of $S^{2-}$ ions in aqueous solution is:

1. $5\times {10}^{-16}M$
2. $1.92\times {10}^{-22}M$
3. $2.6\times {10}^{-24}M$
4. $4.6\times {10}^{-18}M$

Q. For a given aqueous solution at ${25}^{o}C$ which of the following is correct regarding the nature of solution:

1. Acidic if $\left[H^{+}\right]<\sqrt{K_w}$
2. Alkaline if $\left[H^{+}\right]<\sqrt{K_w}$
3. Acidic if $\left[H^{+}\right]>\sqrt{K_w}$
4. Neutral if $\left[H^{+}\right]=\sqrt{K_w}$

Q. The sodium salt of a certain weak monobasic organic acid is hydrolysed to an extent of $3\%$ in its $0.1M$ solution at ${25}^{\circ }\text{C}$. Given that the ionic product of water is ${10}^{-14}$ at this temperature, what is the dissociation constant of the acid ?

1. $1\times {10}^{-10}$
2. $1\times {10}^{-9}$
3. $3.33\times {10}^{-9}$
4. $3.33\times {10}^{-10}$

Q. Two weak bases $AOH$ and $BOH$ having equal concentrations of 1 M are present in solution at ${25}^{o}C$ having dissociation constants as $1\times {10}^{-10}$ and $3\times {10}^{-10}$ respectively. Calculate the ratio $\frac{{\alpha }_1}{{\alpha }_2}$

Here ${\alpha }_1$ is the degree of dissociation of $AOH$
${\alpha }_2$ is degree of dissociation of $BOH$

1. 1.5
2. 1
3. 0.33
4. 0.5

Q. One litre of solution contains ${10}^{-5}$ moles of $H^{+}$ ions at ${25}^{\circ }C$ percentage ionisation of water in solution is:

1. $1.8\times {10}^{-7}$ %
2. $1.8\times {10}^{-9}$ %
3. $3.6\times {10}^{-9}$ %
4. $1.8\times {10}^{-11}$%

Q. Assertion:
(A)$\to$When water is heated to ${80}^{\circ }C$ then concentrations $\left[H^{+}\right]and\left[O{H}^{-}\right]$ will increase.
Reason:
(R)$\to K_w$ increases with decrease in temperature.

1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true but R is not the correct explanation of A
3. A is true but R is false
4. Both A and R are false

Q. The dissociation constant of a base $MOH$ is $5.5\times {10}^{-6}$, then calculate the dissociation constant of its conjugate acid.

1. $1.81\times {10}^{-9}$
2. $1.81\times {10}^{-8}$
3. $2.81\times {10}^{-7}$
4. $2.81\times {10}^{-8}$

Q. Calculate $\left[O{H}^{-}\right]$ of 0.01 M ammonium hydroxide solution. The ionization constant for $N{H}_{4}OH$ is $1.8\times {10}^{-5}M$.

1. $7.84\times {10}^{-4}M$
2. $0.88\times {10}^{-5}M$
3. $1.56\times {10}^{-5}M$
4. $4.24\times {10}^{-4}M$

Q. $H_{3}A$ is a weak triprotic acid $(K{a}_1={10}^{-5},K{a}_2={10}^{-9},K{a}_3={10}^{-13}).$
What is the value of $pX$ of $0.1M{H}_{3}A\left(aq\right)$ solution?
Given $pX=-logX$ and $X=\frac{\left[A^{3-}\right]}{\left[H{A}^{2-}\right]}$.

1. 7
2. 8
3. 9
4. 10

Q. Consider a solution of two weak acids $W{A}_1$ and $W{A}_2$.
Which of the following statement(s) is/are correct?

1. These two acids will dissociate less than in their individual solutions of the same concentration.
2. Common ion effect is not observed in case of mixture of two weak acids.
3. These two acids will dissociate more than in their individual solutions of the same concentration.
4. Common ion effect is observed in case of a mixture of two weak acids.

Q. 0.2(M) solution of monobasic acid is dissociated to $0.95\%$ calculate its dissociation constant.
C = 0.2 M

1. $1.6\times {10}^{-4}$
2. $1.8\times {10}^{-5}$
3. $2\times {10}^{-4}$
4. $1.7\times {10}^{-5}$

Q. The initial rate of hydrolysis of methyl acetate (1M) by a weak acid (HA, 1M) is 1/100th of that of a strong acid (HX, 1M), at ${25}^{o}C.$ The $K_a$ of HA is

1. $1\times {10}^{-4}$
2. $1\times {10}^{-5}$
3. $1\times {10}^{-6}$
4. $1\times {10}^{-3}$