Kohlrausch Law

Q. At ${25}^{o}C$, the specific conductance of $0.01M$ aqueous solution of acetic acid is $1.63\times {10}^{-2}S{m}^{-1}$ and the molar conductance at infinite dilution is $390.7\times {10}^{-4}S{m}^{2}mo{l}^{-1}$. Calculate the dissociation constant $\left(K_a\right)$ of the acid.

1. $2.5\times {10}^{-3}mold{m}^{-5}$
2. $1.2\times {10}^{-3}mold{m}^{-5}$
3. $9.8\times {10}^{-5}mold{m}^{-3}$
4. $1.82\times {10}^{-5}mold{m}^{-3}$

Q.

How nickel is extracted by mond's process?

Q.

Why does the conductivity of a solution decrease with dilution?

Q.

pH of 0.1 molar monobasic acid is found to be 2. Hence its osmotic pressure at given temperature T is (T is in Kelvin scale)

Q. The molar conductance of sodium acetate$\left(C{H}_{3}COONa\right)$, hydrochloric acid$\left(HCl\right)$ and sodium chloride$\left(NaCl\right)$ at infinite dilution are $91.0\times {10}^{-4},426.16\times {10}^{-4}\text{and}126.45\times {10}^{-4}S{m}^{2}mo{l}^{-1}$ respectively, at ${25}^{\circ }C$. Calculate the molar conductance at infinite dilution of for acetic acid:

1. $290.62\times {10}^{-4}S{m}^{2}mo{l}^{-1}$
2. $390.71\times {10}^{-4}S{m}^{2}mo{l}^{-1}$
3. $280.00\times {10}^{-4}S{m}^{2}mo{l}^{-1}$
4. $300.45\times {10}^{-4}S{m}^{2}mo{l}^{-1}$

Q.

$5.00mL$ of $0.10M$ oxalic acid solution taken in a conical flask is titrated against $\mathrm{NaOH}$ from a burette using phenolphthalein indicator. The volume of $\mathrm{NaOH}$ required for the appearance of permanent faint pink color is tabulated below for five experiments. What is the concentration, in molarity, of the $\mathrm{NaOH}$ solution?

Experiment number	Volume of $\mathrm{NaOH}$ (mL)
$1$	$12.5$
$2$	$10.5$
$3$	$9.0$
$4$	$9.0$
$5$	$9.0$

Q. The molar conductance at infinite dilution of $BaC{l}_2$, $NaCl$, $NaOH$ are
$280\times {10}^{-4}$, $126.5\times {10}^{-4}$, $248\times {10}^{-4}S{m}^{2}mo{l}^{-1}$ respectively. The molar conductance at infinite dilution for $Ba(OH{)}_2$ is:

1. $523\times {10}^{-4}S{m}^{2}mo{l}^{-1}$
2. $52.3\times {10}^{-4}S{m}^{2}mo{l}^{-1}$
3. $65\times {10}^{-4}S{m}^{2}mo{l}^{-1}$
4. $5.23\times {10}^{-4}S{m}^{2}mo{l}^{-1}$

Q.

What is the effect of dilution on degree of dissociation of weak electrolyte ?

Q.

The conductivity of an electrolytic solution decreases on dilution due to the?

Q.

State the Kohlrausch law of independent migration of ions. Give an expression for the molar conductivity of acetic acid at infinite dilution.

Q. Ionic conductance of infinite dilution of Al3+ and So4^2- are 189 and 160 ohm^-1 cm^2 mol^-1 respectively. Calculate the molar conductance of Agso4^2-.

Q.

Which among the following statement(s) is(are) true for the extraction of Aluminium from Bauxite?

1. Hydrated ${\mathrm{Al}}_2{\mathrm{O}}_3$ precipitates, when ${\mathrm{CO}}_2$ is bubbled through a solution of Sodium aluminate.

2. The addition of ${\mathrm{Na}}_3{\mathrm{AlF}}_6$ lowers the melting point of Alumina.

3. ${\mathrm{CO}}_2$ evolved at the anode during electrolysis.

4. The cathode is a steel vessel with a lining of Carbon.

Q. 23. For HCl solution, at 25 ^° C the equivalent conductivity at infinite dilution is 425 cm2/ohm equi .the specific conductance of a solution of HCl is 3.825/ ohm cm .if the apparent degree of dissociation is 90% .the normality of the solution is

Q. The equivalent conductivity of acetic acid at infinite dilution is $370Sc{m}^{2}e{q}^{-1}$. At the same temperature, 0.001 M solution of acetic acid, it is $55.5Sc{m}^{2}e{q}^{-1}$. What is the degree of dissociation of 0.1 N acetic acid? (Assume $1-\alpha \approx 1$)

1. $0.15\%$
2. $0.0015\%$
   
3. $15\%$
4. $1.5\%$
   

Q. at 25 degree celsius the molar conductance at infinite dilution for HCl solution is 4.25*10-2 ohm- m2 mol- , while its specific conductanceis 382.5 ohm m- . if degree of dissociation is 90% , the molarity of the solution is

Q. Which one of the following does not correctly represent the correct order of the property indicated against it ?

1. $Ti<V<Cr<Mn$ ; increasing number of oxidation states
2. $Ti<V<Mn<Cr$; increasing $2^{nd}$ ionization enthalpy
3. $T{i}^{3+}<V^{3+}<C{r}^{3+}<M{n}^{3+}$; increasing magnetic moment
4. $Ti<V<Cr<Mn$ ; increasing melting points

Q.

Hydrogen peroxide is used for the preparation of oxygen gas in the laboratory.

1. True
2. False

Q.

If $S(p,q,r)=(~p)\vee [~(q\wedge r\left)\right]$ is a compound statement, then $S(~p,~q,~r)$ is

1. $~S(p,q,r)$

2. $S(p,q,r)$

3. $p\vee (q\wedge r)$

4. $p\wedge (q\vee r)$

5. $S(p,q,~r)$

Q. Given that $\left(inSc{m}^{2}e{q}^{-1}\right)$ at $\text{T}=298\text{K}{\Lambda }_{eq}^{\circ }$ for $Ba(OH{)}_2,BaC{l}_2\text{and}N{H}_{4}Cl$ are 228.8, 120.3 and 129.8 respectively. Specific conductance for 0.2 $N$ $N{H}_{4}OH$ solution is $4.766\times {10}^{-4}{\text{Scm}}^{-1}$, then the $pH$ of given $N{H}_{4}OH$ solution will be:

1. 11.3
2. 7.9
3. 9.2
4. 12.1

Q. A conductivity cell, when filled with an aqueous solution of $0.02M$ $KCl$ at $25°C$, had a resistance of $250\text{ohm}$. Its resistance, when filled with $6\times {10}^{-5}MN{H}_{4}OH$ solution was ${10}^5$ $\text{ohm}$. The specific conducatnce of $0.02M$ $KCl$ was $0.277S{m}^{-1}$. The molar ionic conductances at infinite dilution of $N{H}_4^{+}\text{and}O{H}^{-}\text{ions are}73.4\times {10}^{-4}\text{and}198.0\times {10}^{-4}S{m}^{2}mo{l}^{-1},$ respectively. Calculate the degree of dissociation of $6\times {10}^{-5}MN{H}_{4}OH$ solution:

1. 0.424
2. 0.845
3. 0.954
4. 0.765

Q.

What is the $\mathrm{pH}$ of millimolar solution of ammonium hydroxide which is $20\%$ dissociated?

Q. According to Kohlrausch’s law, conductivity of ions at infinite dilutions does not depend on

1. temperature
2. nature of co-ions
3. pressure
4. concentration

Q.

Kohlrausch's Law shows that:

1. at infinite dilution the concentration of ions increases.

2. at infinite dilution the ionic conductivity of all the ions of the electrolyte become equal.

3. at infinite dilution the ionic conductivity of ions is additive.

4. at infinite dilution the concentration of the electrolyte becomes unity.

Q. The ionization constant of a weak acid is $1.6\times {10}^{-5}$ and the molar conductivity at infinite dilution is $380\times {10}^{-4}S{m}^{2}mo{l}^{-1}.$ If the cell constant is $0.01m^{-1}$ then conductance of $0.01M$ acid solution is :

1. 
   $1.52\times {10}^{-5}S$
2. 
   $1.52S$
3. 
   $1.52\times {10}^{-3}S$
4. 
   $1.52\times {10}^{-4}S$

Q. Molar conductance is used to define as the conducting power of all the ions produced by one mole of the electrolyte in the given solution.
$\Lambda m=\frac{1000\times K}{C}$
Where, K = specific conductance, C = Molar concentration of the solution.
At infinite dilution, each ion makes a definite contribution for the conductance of electrolyte. At infinite dilution, the molar conductance of an electrolyte is the sum of the ionic conductance of constituent ions.
$\Lambda A{B}_m^{\infty }=x{A}_{+}^{\infty }+y{A}_{+}^{\infty }$ where, x and y are the number of cations and anions per formula unit of the electrolyte. By measuring the conductance we can measure degree of dissociation and dissociation constants.
$\alpha =\frac{{\Lambda }^C}{{\Lambda }^{\infty }};K_a=\frac{a^{2}C}{(1-\alpha )};K_b=\frac{{\alpha }^{2}C}{(1-\alpha )}$
By conductance measurements we can calculate the solubility product of a sparingly soluble salt. For a sparingly soluble salt, the saturated solution will be an extremely dilute solution and $A^C$ is taken as $A^{\infty }$. Knowing $A^{\infty }$ (by Kohlrausch’s law) the concentration of saturated solution is calculated from which Ksp is calculated.
The degree of dissociation of water will be
$({\Lambda }_{H^{+}}^0=3.458\times {10}^{-2}S{m}^{2}mo{l}^{-1};{\Lambda }_{O{H}^{-}}^0=1.98\times {10}^{-2}S{m}^{2}mo{l}^{–1};Kaofwater=5.7\times {10}^{-6}S{m}^{-1})$

1. $1.875\times {10}^{-7}\%$
2. $2.165\times {10}^{-5}\%$
3. $3.457\times {10}^{-2}\%$
4. $1.27\%$

Q. The equivalent conductance of an infinitely dilute solution of $N{H}_{4}Cl$ is $150$ and the ionic conductance of $O{H}^{–}$ and $C{l}^{–}$ ions are $198$ and $76$ respectively. If the equivalent conductance of a $0.01N$ solution of $N{H}_{4}OH$ is $9.6$, what will be its degree of dissociation?

1. $0.96$
2. $0.0103$
3. $0.414$
4. $0.0353$

Q. The ionic conductance of $B{a}^{2+}$ and $C{l}^{-}$ are respectively $127$ and $76oh{m}^{-1}c{m}^{2}mo{l}^{-1}$ at infinite dilution. The equivalent conductance (in $oh{m}^{-1}c{m}^{2}e{q}^{-1}$) of $BaC{l}_2$ at infinite dilution will be:

1. $203$
2. $139.5$
3. $279$
4. $101.5$

Q. Absolute ionic mobility is the speed of the ion under the electric field of ?

1. 5 V across a distance of 10 cm
2. 5 V across a distance of 15 cm
3. None of these
4. 10 V across a distance of 5 cm

Q. ${\wedge }_m^{\circ }\left(N{H}_{4}OH\right)$ is equal to

1. ${\wedge }_m^{\circ }\left(N{H}_{4}OH\right)+{\wedge }_m^{\circ }\left(N{H}_{4}Cl\right)-{\wedge }_m^{\circ }\left(HCl\right)$
2. ${\wedge }_m^{\circ }\left(N{H}_{4}Cl\right)+{\wedge }_m^{\circ }\left(NaOH\right)-{\wedge }_m^{\circ }\left(NaCl\right)$
3. ${\wedge }_m^{\circ }\left(N{H}_{4}Cl\right)+{\wedge }_m^{\circ }\left(NaCl\right)-{\wedge }_m^{\circ }\left(NaOH\right)$
4. ${\wedge }_m^{\circ }\left(NaOH\right)+{\wedge }_m^{\circ }\left(NaCl\right)-{\wedge }_m^{\circ }\left(N{H}_{4}Cl\right)$

Q. According to Kohlrausch’s law, conductivity of ions is constant at

1. all the concentrations
2. 1 M concentration
3. infinite dilution
4. fixed temperature