Question

Acidified water was electrolysed using an inert electrode and volume of gases liberated at STP was 168mL.The amount of electricity passed through water was
A) ${96500^0}$
B) ${9650^0}$
C) ${965^0}$
D) ${168^0}$

Answer 1

Hint: In this question we need to determine the amount of electricity which is passed through water. For this, students need to know and use Faraday’s law of electrolysis and use the formula to solve the questions.

Complete step-by-step answer:
Electrolysis: It is a phenomenon by which the elements are broken from their compounds and deposited at the electrodes. Cations are reduced at cathode and anions are oxidised at anion.
Faraday's First Law of Electrolysis expresses that the chemical deposition because of the progression of flow through an electrolyte is straightforwardly relative to the amount of power (coulombs) went through it.
$
  m\;\alpha \;quantity\;of\;electricity,Q \\
   \Rightarrow m = Z.Q \\
 $
Where, Z is a constant of proportionality and is known as the electro-chemical equivalent of the substance.

Faraday’s second law of electrolysis states that, when the same quantity of electricity is passed through several electrolytes, the mass of the substances deposited are proportional to their respective chemical equivalent or equivalent weight.
$2{H_2}O \to 2{H_{2(g)}} + {O_{2(g)}}$

$2{H_2}O$	$2{H_{2(g)}}$	${O_{2(g)}}$
0.168	2x	x

\[
  3x = 0.168 \\
   \Rightarrow x = \dfrac{{0.168}}{3} \\
   \Rightarrow x = 0.056 \\
 \]
Therefore,
The volume of Hydrogen is,
$
\Rightarrow {V_{{H_{2(g)}}}} = 2x \\
   = 2 \times 0.056 \\
   = 0.112\;L \\
 $
Similarly,
The volume the oxygen is,
$
\Rightarrow {V_{{O_{2(g)}}}} = x \\
   = 0.056\;L \\
 $
11.2L of ${H_2}$ at STP=1F
Then, 0.112L of ${H_2}$ at STP=0.01F
Also, 0.056L of ${H_2}$ at STP=0.01F
Therefore, the amount of electricity passed = 0.01F = 965 degree Celsius

Additional Information: STP was defined as a temperature of 273.15 K (0 °C, 32 °F) and an absolute pressure of exactly 1 atmosphere (101.325 kPa).

Hence from the above solution option C is correct.

Note: When it comes to comparison, the atmospheric pressure at the top of Mount Everest is\[0.36{\text{ }}atm\]. This means that if anyone plans to boil water at the top of Mount Everest, it is more likely to boil faster at that altitude. Thus we can state that the boiling point is the temperature at which the vapour pressure of that substance equals the atmospheric pressure.