Factors Affecting Alpha

Q. The plot given below shows P - T curves (where P is pressure and T is the temperature) for two solvents X and Y and isomolal solutions of $NaCl$ in these solvents. $NaCl$ completely dissociates in both the solvents.

On addition of equal number of moles of a non-volatile solute S in equal amount (in kg) of these solvents, the elevation of boiling point of solvent X is three times than that of solvent Y. Solute S is known to undergo dimerization in these solvents. If the degree of dimerization is 0.7 in solvent Y, the degree of dimerization in solvent X is:

Q.

Which of the following is the strongest acid ?

1. H₂SO₃

2. H₂SO₄

3. HClO₄

4. H₃PO₄

Q. Percentage ionization of weak acid can be calculated using the formula:

1. $100\sqrt{\frac{K_a}{C}}$
2. $\frac{100}{1+{10}^{(p{K}_a-pH)}}$
3. Both (a) and (b)
4. none

Q. $\text{The gas phase reaction},$
$2A\left(g\right)\to A_2\left(g\right)$ $\text{at}400K\text{has}\Delta G^{\circ }=+25.2kJmo{l}^{–1}$
The equilibrium constant, $K_C$ for this reaction is ______ × ${10}^{-2}$ (Round off to the Nearest Integer).

[Use : $R=8.3Jmo{l}^{–1}{K}^{–1}$, ln 10 = 2.3
$lo{g}_{10}2=0.30,1atm=1bar$]
[antilog (– 0.3) = 0.501]

Q. A weak acid HX has the dissociation constant $1\times {10}^{-5}M.$ It forms a salt NaX on reaction with alkali. The percentage degree of hydrolysis of 0.1 M solution of NaX is:

1. 0.0001 %
2. 0.01 %
3. 0.1%
4. 0.15 %

Q. The concentration of formate ion $\left(HCO{O}^{-}\right)$ present in 0.1 M formic acid $\left(HCOOH\right)$ solution at equilibrium is :
$(K_a=1.6\times {10}^{-4})$

1. $4\times {10}^{-3}M$
2. $3\times {10}^{-6}M$
3. $1.5\times {10}^{-3}M$
4. $5\times {10}^{-6}M$

Q. When 0.1 mol of ammonia $\left(N{H}_3\right)$ is dissolved in sufficient water to make 1 L of solution, the solution is found to have a hydroxide ion $\left(O{H}^{-}\right)$ concentration of $1.5\times {10}^{-3}M$ . The value of $K_b$ for $N{H}_3$ is:

1. $0.5\times {10}^{-3}M$
2. $2.28\times {10}^{-5}M$
3. $8.65\times {10}^{-2}M$
4. $5.75\times {10}^{-6}M$

Q. For the reversible reaction, $N_2\left(g\right)+3H_2\left(g\right)\rightleftharpoons 2N{H}_3\left(g\right)$ at ${500}^{o}C,$ the value of $K_p$ is $1.44\times {10}^{-5}$, when partial pressure is measured in atmosphere. The corresponding value of $K_c,$ with concentration in $mol{L}^{-1},$ is

1. $\frac{1.44\times {10}^{-5}}{(0.082\times 500{)}^{-2}}$
2. $\frac{1.44\times {10}^{-5}}{(8.314\times 773{)}^{-2}}$
3. $\frac{1.44\times {10}^{-5}}{(0.082\times 773{)}^2}$
4. $\frac{1.44\times {10}^{-5}}{(0.082\times 773{)}^{-2}}$

Q. Calculate the $pH$ of solution when $100\text{mL}$, $0.1\text{M}$ $C{H}_{3}COOH$ and $100\text{mL}$, $0.1\text{M}HCOOH$ are mix together (Given : $K_a\left(C{H}_{3}COOH\right)=2\times {10}^{-5},K_a\left(HCOOH\right)=6\times {10}^{-5})$ (Given: $\log 2=0.30$)

Q. A buffer solution can be prepared from a mixture of:
(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), (ii), (iii)
2. (ii), (iii)
3. (iii), (iv)
4. (i), (iii)

Q.

On addition of ammonium chloride to a solution of ammonium hydroxide

1. Dissociation of NH₄OH increases

2. Concentration of OH^- increases

3. Concentration of OH^- decreases

4. Concentration of NH₄⁺ and OH^- increases

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

Q. The $p{K}_a$ values of four carboxylic acids are given below. Identify the weakest carboxylic acid.

1. 4.89
2. 1.28
3. 4.76
4. 2.56

Q. An aqueous solution of a salt $M{X}_2$ at certain temperature has a van't Hoff factor of $2$. The degree of dissociation for this solution of the salt is:
(JEE Main - 2016)

1. $0.67$
2. $0.33$
3. $0.50$
4. $0.80$

Q. what is the concentration of chloride ions in the mixture of 500ml , 1M NaCl solution and 500 ml , 1M CaCl2 solution

Q. When 0.1 mole solid NaOH is added in 1 lt of 0.1 M $N{H}_3\left(aq\right)$ then which statement is wrong? $(K_b=2\times {10}^{-5},\log 2=0.3)$

1. Degree of dissociation of $N{H}_3$ approaches to zero.
2. On addition of $O{H}^{-}{K}_b$ of $N{H}_3$ does not changes.
3. Change in pH by adding NaOH would be 1.85
4. In solution, $\left[N{a}^{+}\right]=0.1M,\left[N{H}_3\right]=0.1M,\left[O{H}^{-}\right]=0.2M.$

Q. For $A\left(g\right)\rightleftharpoons 2B\left(g\right)$, equilibrium constant at total equilibrium pressure $p_1$ is $K_{P_1}\text{and for C(g)}\rightleftharpoons D\left(g\right)+E\left(g\right),$
equilibrium constant at total equilibrium pressure $P_2$ is $K_{p2}.$ If degree of dissociation of A and C are same, then the ratio $K_{P_1}/K_{P_2},$ if $2P_1=P_2,$ is:

1. 2
2. $\frac{1}{8}$
3. $\frac{1}{2}$
4. 8

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

1. $1.1\times {10}^{-10}$
2. $1.1\times {10}^{-9}$
3. $3.33\times {10}^{-9}$
4. $3.33\times {10}^{-10}$

Q. The pH of $0.05M$ aqueous solution of diethyl amine is 12.0. Calculate $K_b$.

1. $2.5\times {10}^{-4}$
2. $5\times {10}^{-3}$
3. $2.5\times {10}^{-3}$
4. $5\times {10}^{-4}$

Q.

The pH of 0.1M solution of cyanic acid (HCNO) is 2.34. Calculate the ionization constant of the acid and its degree of ionization in the solution.

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. 8
2. 7
3. 9
4. 10

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

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. A solution is saturated with $SrC{O}_3$ and $Sr{F}_2$. The $\left[C{O}_3^{2-}\right]$ is found to be $1.2\times {10}^{-3}M.$ if the value of solublity product of $SrC{O}_3$ and $Sr{F}_2$ are $7.0\times {10}^{-10}and7.9\times {10}^{-9}$ resectively.The concentration of $F^{-}$ in the solution would be

1. $3.7\times {10}^{-6}M$
2. $3.2\times {10}^{-3}M$
3. $3.7\times {10}^{-2}M$
4. $5.1\times {10}^{-7}M$

Q. What is the pH of a 1.0 M solution of acetic acid? To what volume of one litre of this solution be diluted so that the pH of resulting solution will be twice the original value? Given $K_a$=1.8 $\times {10}^{-5},lo{g}_{10}4.2426\times {10}^{-3}=2.3724$

1. $2.78\times {10}^4\text{litre}$
2. $2.78\times {10}^2\text{litre}$
3. $3.68\times {10}^5\text{litre}$
4. $3.68\times {10}^2\text{litre}$

Q.

An ionizing solvent has

1. Low value of dielectric constant

2. High value of dielectric constant

3. A dielectric constant equal to 1

4. Has a high melting point

Q. An aqueous solution contains $0.10M{H}_{2}S$ and $0.20MHCl$. 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 ions $H{S}^{-}$ is $1.2\times {10}^{-13}$ then the concentration of $S^{2-}$ ions in aqueous solution is:

1. $6\times {10}^{-21}$
2. $5\times {10}^{-8}$
3. $5\times {10}^{-19}$
4. $3\times {10}^{-20}$

Q.

$2{\mathrm{Br}}^{-}+{\mathrm{H}}_2{\mathrm{O}}_2+2{\mathrm{H}}^{+}\to {\mathrm{Br}}_2+2{\mathrm{H}}_2\mathrm{O}$ Rate =$\mathrm{k}\left({\mathrm{H}}_2{\mathrm{O}}_2\right)\left({\mathrm{H}}^{+}\right)\left({\mathrm{Br}}^{-}\right)$ What is the effect on rate constant on increasing bromide ions?

Q. Which one is the correct order of acidity?

1. $C{H}_2=C{H}_2>C{H}_3-CH=C{H}_2>C{H}_3-C\equiv CH>CH\equiv CH$
2. $CH\equiv CH>C{H}_3-C\equiv CH>C{H}_2=C{H}_2>C{H}_3-C{H}_3$
3. $CH\equiv CH>C{H}_2=C{H}_2>C{H}_3-C\equiv CH>C{H}_3-C{H}_3$
4. $C{H}_3-C{H}_3>C{H}_2=C{H}_2>C{H}_3-C\equiv CH>CH\equiv CH$

Q. $PC{l}_5$ dissociates as $PC{l}_5\left(g\right)\rightleftharpoons PC{l}_3\left(g\right)+C{l}_2\left(g\right).$ If total pressure at equilibrium of the reaction mixture is P and degree of dissociation of $PC{l}_5$ is x, the partial pressure of $PC{l}_3$ will be:

1. $\left(\frac{x}{1+x}\right)\times P$
2. $\left(\frac{x}{1+x}\right)\times P$
3. $\left(\frac{2x}{1+x}\right)\times P$
4. $x\times P$