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QUESTION: 1

The unit of molar conductivity is:

Solution:

- The molar conductivity of an electrolytic solution is the conductance of the volume of the solution containing a unit mole of electrolyte that is placed between two electrodes of unit area cross-section or at a distance of one-centimeter apart.
- The unit of molar conductivity is
**S⋅m**.^{2}⋅mol^{-1}

QUESTION: 2

The cell constant of a conductivity cell is defined as:

Where l = distance between electrodes and A = area of cross-section of each of the electrodes

Solution:

- The cell constant is a multiplier constant specific to a conductivity sensor.
- The measured current is multiplied by the cell constant to determine the electrical conductivity of the solution.
- The cell constant, known as K, refers to a theoretical electrode consisting of two 1 cm square plates 1 cm apart.
- A cell constant has units of 1/cm (per centimeter), where the number refers to the
**ratio of the distance between the electrode plates to the surface area of the plate**.

QUESTION: 3

Molar conductivity is defined as:

Where k = conductivity, G = conductance, l = distance between two electrodes and V_{m} = volume of solution containing 1 mol of electrolyte

Solution:

- The molar conductivity of an electrolytic solution is the
**conductance of the volume of the solution containing a unit mole of electrolyte that is placed between two electrodes of unit area cross-section**or at a distance of one-centimeter apart.

Where C = concentration of electrolyte

QUESTION: 4

For a dilute solution of a strong electrolyte, the variation of molar conductivity with concentration is given by:

Solution:

QUESTION: 5

Which of the following ion is expected to have least value of molar conductivity at infinite dilution in an aqueous solution:

Solution:

- Na
^{+}has lower molar conductance than the ions that are greater in size than Na such as K+, Cs+ as the**molar conductance is inversely proportional to the solvation of ions**. - Smaller the ion, the greater will be the solvation, and hence lower will be the molar conductance.

QUESTION: 6

Which of the following ion is expected to have highest value of molar conductivity at infinite dilution in an aqueous solution:

Solution:

H^{+} ions will have the maximum molar conductivity amongst the given cations due to **Grothus conduction**.

QUESTION: 7

The degree of dissociation of a weak electrolyte is given by:

Solution:

QUESTION: 8

Which of the following ion has highest molar conductivity at infinite dilution in an aqueous solution:

Solution:

Exceptionally high values are found for H^{+} (349.8 S·cm^{2}/mol) and OH^{−} (198.6 S·cm^{2}/mol), which are explained by the **Grotthuss proton-hopping mechanism** for the movement of these ions.

QUESTION: 9

The equilibrium constant of acetic acid in an aqueous solution of concentration C is given by

Solution:

QUESTION: 10

Molar conductivity of Fe_{2}(SO_{4})_{3} is given by:

Solution:

QUESTION: 11

Equivalent conductivity of Fe_{2}(SO_{4})_{3} is related to molar conductivity by the expression:

Solution:

QUESTION: 12

Which of the following expressions is correct:

Solution:

According to **kholaraus law**,

NH_{4}OH = NH_{4} + OH

i.e. NH_{4} + Cl + Na + OH – Na – Cl = NH_{4}Cl + NaOH - NaCl

QUESTION: 13

If x is the specific resistance of the electrolyte solution and y is he molarity of the solution, then is given by:

Solution:

Molar conductivity is defined as the conductivity of an electrolyte solution divided by the molar concentration of electrolyte.

∧_{m }= (k × 1000)/M

= 1/x × 1000/y

= 1000/xy

QUESTION: 14

When a conductance cell was filled with a 0.0025 M solution of K_{2}SO_{4}, its resistance was 326 Ω. If cell constant is 0.2281 cm^{-1}, the specific conductance (Ω^{-1}cm^{-1}) of K_{2}SO_{4} solution is:

Solution:

QUESTION: 15

Equivalent conductance of 0.1 M HA (weak acid) solution is 10 cm^{2} equivalent^{–1}. The pH of HA solution is(molar conductivity at infinite dilution is 200).

Solution:

QUESTION: 16

For HCl solution at 25ºC, the equivalent conductivity at infinite dilution is 425 Ω^{-1} cm^{2} eq^{-1}. The specific conductance of a solution of HCl is 3.825 Ω^{-1} cm^{-1}. If the apparent degree of dissociat ion is 90%, the normality of solution is

Solution:

QUESTION: 17

The conductance at infinite dilution follow the order

Solution:

- Smaller the ion, the greater will be the solvation, and hence lower will be the molar conductance.

QUESTION: 18

The correct relation which depicts the Debye-Huckel Onsager Theory for strong electrolytes is:

Solution:

- The Debye-Huckel was proposed by Peter Debye and Erich Huckel as a theoretical explanation for departure from ideality in solutions of electrolytes, further modified by Lars Onsager in 1927.
- Onsager was able to derive a theoretical expression to account for the empirical relation known as
**Kohlrausch's law for the molar conductivity**,

Am = Am_{o}- K(c)^{½}

__For stronger electrolytes:__

A_{m} = A_{m}^{o} - (A + BAm_{o})(c)^{1/2ac}

QUESTION: 19

The unit of A in Debye-Huckel-Onsager equation for strong electrolytes is:

Solution:

QUESTION: 20

Which of the following solutions will show the minimum value of transference number of Cl^{–1} ions:

Solution:

- Because t
_{H}^{+}has a maximum value of transference no. as compared to other cations. - Hence, t
_{Cl}^{-}will be minimum in 0.1 M HCl solution.

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