Kohlrausch Law

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

Q. During the discharge of a lead storage battery the density of sulphuric acid fell from $1.294$ to $1.139{\text{g mL}}^{-1}$ . $H_{2}S{O}_4$ of density $1.294{\text{g mL}}^{-1}$ is 39% and that of density $1.139{\text{g mL}}^{-1}$ is 20% by weight. The battery holds $3.5\text{L}$ of acid and the volume practically remains constant during the discharge. Calculate the number of Ampere hours for which the battery must have been used. The discharging reactions are:
$Pb+S{O}_4^{2-}\to PbS{O}_4+2e^{-}\left(\text{anode}\right)$
$Pb{O}_2+4H^{+}+S{O}_4^{2-}+2e^{-}\to PbS{O}_4+2H_{2}O\left(\text{cathode}\right)$

1. $190$
2. $530$
3. $132.5$
4. $265$

Q. Calculate simultaneous solubility of silver thiocyanate $\left(AgSCN\right)$and silver bromide $\left(AgBr\right)$ in water respectively.
Given that $K_{sp}$ of silver thiocyanate = ${10}^{-12}$ and $K_{sp}$ of silver bromide $=5\times {10}^{-13}$ .

1. $4.16\times {10}^{-7}M$ and $2.08\times {10}^{-7}M$
2. $2.08\times {10}^{-12}M$ and $4.16\times {10}^{-12}M$
3. $5.08\times {10}^{-9}M$ and $9.16\times {10}^{-9}M$
4. $8.16\times {10}^{-7}M$ and $4.08\times {10}^{-7}M$

Q. The molar conductivity of $0.007M$ acetic acid is $20Sc{m}^{2}mo{l}^{-1}$. What is the dissociation constant of acetic acid ? choose the correct option.
$\left[\begin{array}{c}{\Lambda }_{H^{+}}^{\circ }=350Sc{m}^{2}mo{l}^{-1}\\ {\Lambda }_{C{H}_{3}CO{O}^{-}}^{\circ }=50Sc{m}^{2}mo{l}^{-1}\end{array}\right]$

(NEET 2021)

Q.

State the Kohlrausch law of independent migration of ions. Why does the conductivity of a solution decrease with dilution?

Q. Assertion: If ${\lambda }_{N{a}^{+}}^{\circ }+{\lambda }_{C{l}^{-}}^{\circ }$ are molar limiting conductivity of the sodium and chloride ions respectively, then the limiting molar conducting for sodium chloride is given by the equation: ${\lambda }_{NaCl}^{\circ }={\lambda }_{N{a}^{+}}^{\circ }+{\lambda }_{C{l}^{-}}^{\circ }$
Reason:This is according to Kohlrausch law of independent migration of ions.

1. If both assertion and reason are true and the reason is the correct explanation of the assertion.
2. If both assertion and reason are true but reason is not the correct explanation of the assertion.
3. If assertion is true but reason is false.
4. If the assertion and reason both are false.

Q. Assertion: If ${\lambda }_{N{a}^{+}}^{\circ }+{\lambda }_{C{l}^{-}}^{\circ }$ are molar limiting conductivity of the sodium and chloride ions respectively, then the limiting molar conducting for sodium chloride is given by the equation: ${\lambda }_{NaCl}^{\circ }={\lambda }_{N{a}^{+}}^{\circ }+{\lambda }_{C{l}^{-}}^{\circ }$
Reason:This is according to Kohlrausch law of independent migration of ions.

1. If both assertion and reason are true and the reason is the correct explanation of the assertion.
2. If both assertion and reason are true but reason is not the correct explanation of the assertion.
3. If assertion is true but reason is false.
4. If the assertion and reason both are false.

Q. The specific conductance of $0.01M$ solution of acetic acid was found to be $0.0163S{m}^{-1}$ at $25{}^{o}C$. Calculate the degree of dissociation of the acid.
Molar conductance of acetic acid at infinite dilution is $390.7\times {10}^{-4}S{m}^{2}mo{l}^{-1}$ at $25{}^{o}C$.

1. $0.0417$
2. $0.0823$
3. $0.0632$
4. $0.0984$

Q. The limiting molar conductivities ${\lambda }^{\circ }$ for $NaCl,KBr$ and $KCl$ are $126,152$ and $150Sc{m}^{2}mo{l}^{-1}$respectively. The ${\lambda }^{\circ }$ for $NaBr$ is

1. $278Sc{m}^{2}mo{l}^{-1}$
2. $176Sc{m}^{2}mo{l}^{-1}$
3. $128Sc{m}^{2}mo{l}^{-1}$
4. $302Sc{m}^{2}mo{l}^{-}1$

Q. Degree of dissociation $\alpha$ =

1. $\frac{{\wedge }_m}{{\wedge }_m^{\circ }}$
2. $\frac{{\wedge }_m^{\circ }}{{\wedge }_m}$
3. ${\wedge }_m-{\wedge }_m^{\circ }$
4. $\sqrt{{\wedge }_m}-\sqrt{{\wedge }_m^{\circ }}$

Q. The molar conductivities at infinite dilution of $AgN{O}_3$ and $NaCl$ are 116.0 and 110.0 $Sc{m}^{2}mo{l}^{-1}$ respectively. The conductivity of $AgCl$ in water is $8.42\times {10}^{-6}Sc{m}^{–1}$ and of water used is $1.16\times {10}^{-6}Sc{m}^{–1}$. The solubility of $AgCl$ is $6.0\times {10}^{-5}mol/L$. Find the molar conductivity at infinite dilution of $NaN{O}_3$ ($inSc{m}^{-1}mo{l}^{-1}$) in the solution.

Q.

Which of the following statements is correct for a strong electrolyte :

1. ${\lambda }_m$ increases linearly with $C^{\frac{1}{2}}$

2. ${\lambda }_m$ increases linearly with $C^2$

3. ${\lambda }_m$ decreases linearly with $C^2$

4. ${\lambda }_m$ decreases linearly with $C^{\frac{1}{2}}$

Q. At $25{}^{\circ }C$molar conductance of $0.1$ $\text{molar}$ aqueous solution of ammonium hydroxide is $9.54{\text{ohm}}^{-1}{\text{cm}}^2{\text{mol}}^{-1}$ undertaken by dilution its molar conductance at infinite is $238{\text{ohm}}^{-1}{\text{cm}}^2{\text{mol}}^{-1}$. The percentage degree of ionization of ammonium hydroxide at the same concentration and temperature is:

1. $4.008\%$
2. $2.080\%$
3. $20.800\%$
4. $40.800\%$

Q. At ${25}^{\circ }C$ molar conductance of 0.1 molar aqueous solution of ammonium hydroxide is $9.54oh{m}^{-1}c{m}^{2}mo{l}^{-1}$ and at infinite dilution its molar conductance is $238oh{m}^{-1}c{m}^{2}mo{l}^{-1}$. The degree of ionisation of ammonium hydroxide at the same concentration and temperature is

1. 40.800%
2. 2.080%
3. 4.008%
4. 20.800%

Q. At ${25}^{\circ }C$ molar conductance of 0.1 molar aqueous solution of ammonium hydroxide is $9.54oh{m}^{-1}c{m}^{2}mo{l}^{-1}$ and at infinite dilution its molar conductance is $238oh{m}^{-1}c{m}^{2}mo{l}^{-1}$. The degree of ionisation of ammonium hydroxide at the same concentration and temperature is

1. 4.008%
2. 40.800%
3. 2.080%
4. 20.800%

Q. The limiting molar conductivities ${\lambda }^{\circ }$ for $NaCl,KBr$ and $KCl$ are $126,152$ and $150Sc{m}^{2}mo{l}^{-1}$respectively. The ${\lambda }^{\circ }$ for $NaBr$ is

1. $278Sc{m}^{2}mo{l}^{-1}$
2. $176Sc{m}^{2}mo{l}^{-1}$
3. $128Sc{m}^{2}mo{l}^{-1}$
4. $302Sc{m}^{2}mo{l}^{-}1$