KEAM 2018 Physics and Chemistry Paper

Total charge produced by cell
=1A×(5951×3600)s
=2142360C
∵96500C=1mol
∴‌‌2142360C=‌

2142360

96500

=22.20mol of e−
Now, in H2−O2, fuel cell following reaction occurs,
At anode At cathode Overall reaction 2H2(g)+O2(g)⟶2H2O⟨n
Thus, from above reaction it is clear that
2mol of e−≡1mol of H2O
∵22mol of e−≡11mol of H2O
=(11×18)g of H2O
[∵ No. of moles =‌

‌ Weight ‌

‌ Molecular weight ‌

]
=198g or mL of H2O
Now, number of mol of NaOH=‌

5

40

=0.125mol
We know that,
Molarity =‌

‌ No. of moles of solute ‌

‌ Volume of solution (in L) ‌

=‌

0.125

198

×1000=0.63M