SATHEE: Electrochemistry - Result Question 23

Electrochemistry - Result Question 23

####25. In electrolysis of $N a C l$ , when $P t$ electrode is taken, then $H_{2}$ is liberated at cathode while with $H g$ cathode, it forms sodium amalgam. This is because

[2002] (a) $H g$ is more inert than $P t$

(b) More voltage is required to reduce $H^{+}$ at $H g$ than at $P t$

(d) Conc. of $H^{+}$ ions is larger when Pt electrode is taken

Show Answer

Solution:

(b) If mercury is used as cathode, $H^{+}$ ions are not discharged at mercury cathode because mercury has a high over voltage for hydrogen.

In electrolysis of $N a C l$ , following ionisations take place:

$N a C l \to N a^{+} + C l^{-}$

$H_{2} O \to H^{+} + O H^{-}$

$N a^{+}$ and $H^{+}$ ions move towards cathode.

However, only $H^{+}$ ions are discharged more readily than $N a^{+}$ ions because in electrochemical series, hydrogen is lower than sodium.

At cathode : $2 H^{+} + 2 e^{-} ⟶ H_{2} (g)$

If mercury is used as cathode, then $N a^{+}$ ions are discharged at cathode in preference to $H^{+}$ ions, yielding sodium, which dissolves in mercury to form sodium amalgam.

At cathode : $N a^{+} + e^{-} ⟶ N a (s)$

$N a (s) + H g (s) ⟶ N a - H g (s)$

Electrochemistry - Result Question 23

Solution:

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

Mentorship

NCERT Exercise Video Solution

Electrochemistry - Result Question 23

Solution:

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

Mentorship

NCERT Exercise Video Solution

Menu