a. Write Kohlrausch's law equation to find out limiting molar conductivity \( \left(\Lambda_{m}^{0}\right) \) of \( NH _{4} OH \)

Question

Answer the following: 

a. Write Kohlrausch's law equation to find out limiting molar conductivity \( \left(\Lambda_{m}^{0}\right) \) of \( NH _{4} OH \) in terms of limiting molar conductivities of strong electrolytes. 

b. Electrode potential for Mg electrode varies according to the equation \[ E = E ^{0}-\frac{0.059}{2} \log \frac{1}{\left[ Mg ^{2+}\right]} \] Plot a graph between \( E \) and \( \log \left[ Mg ^{2+}\right] \) 

c. Concentration plays an important role during electrolysis. Write the chemical reaction that proceeds at anode at a higher concentration of sulfuric acid during electrolysis.

Answer 1

(a) Kohlrausch's law status that the equivalent conductivity of an electrolyte at infinite is equal to the sum of the conductance of the anions and catrons.

A°m (NH₄OH) = (\(\lambda^\circ\)NH₄⁺⁺\(\lambda^\circ\)cl^-) - (\(\lambda^\circ\)_Na⁺ + \(\lambda^\circ\)cl^-) + (\(\lambda^\circ\)Na + \(\lambda^\circ\)\(\bar O\)H)

or A°m (NH₄OH) = A°m (NH₄cl) - A°m (Nacl) + A°m (NaOH)

(b) E = E° - \(\cfrac{0.059}{2}\)log \(\cfrac{1}{[mg^{2+}]}\)

or E = E° + \(\cfrac{0.059}{2}\) log [mg²⁺]

or E = \(\cfrac{0.059}{2}\) log [mg²⁺] + E°....(1)

equation (1) is similar to the equation of straight line (y = mx + c)

(c) On electrolysis of sulfuric acid, H⁺ ion attract

to wards cathod and \(\bar O\)H (from water) ion attract towards anode.

A⁺ cathode 2H⁺ + 2e^- \(\rightarrow\)H₂ (reduction)

A⁺ anode  4\(\bar O\)H + \(\rightarrow\) O₂ + 2H₂O +4e^- (oxidation)