Question

The total volume of gaseous products obtained at STP by passing two ampere current for 20 min through brine solution is:
a)417.8 ml
b)835.6 ml
c)1253.5 ml
d)1671.3 ml

Answer 1

Have you already written the chemical equation?

Answer 2

*equations
(as you need both half equations)

Answer 3

\(NaCl-->Na^+ + Cl^-\)
\(2Cl^- -->Cl_2 +2e^-\)

\(H_2O-->H^+ + OH^-\)
\(2H^+ +2e^--->H_2\)

At anode: \(Cl_2\) gas is released.
At cathode: \(H_2\) gas is released.

Answer 4

Correct. You can also write in one go:

\(2H_2O+2e^-\rightarrow 2OH^-+H_2\)

Now, how many moles of electrons correspond to 2A for 20 minutes?

Then, how many moles of hydrogen and chlorine will be released?

Then, work out volumes.

Answer 5

\[[\frac{2\times 20 \times 60}{1.6 \times 10^{-19}}]/N_A\]=0.025 moles

So, it will give 0.125 mole each of H2 and Cl2 ?

Answer 6

If you mean 0.0125 mol of each, this is correct.

Better use Faraday's constant \(F=N_A\:e=96485\:C/mol\)
often rounded up to 96500 C/mol

Answer 7

yeah i meant 0.0125 of each.
But it doesn't seem to give me either of the answers.

0.0125 moles of Cl2 and H2 gives a total volume of 2*22.4 * 0.0125 liter=0.56 litre=560 ml.

But it is not in the list of options!

Answer 8

You are right, but I find the same value 560 mL.

Answer 9

Got to go.

Answer 10

ok. thanks!

Answer 11

But It says the answer is (d) 1671.3 ml ...

Answer 12

This would be for one hour.