Question

Silver and copper voltmeters are connected in parallel with a battery of emf 12 V. In 30 min 1 g of silver and 1.8 g of copper are liberated. The energy supplied by the battery is :

• A. 720 J
• B. 2.41 J
• C. 24.12 J
• D. 4.34 $\times$ 10${}^4$ J

Answer 1

Answer: (D)

4.34 $\times$ 10${}^4$ J

Number of moles of silver and copper deposited are $\frac{1}{108}$ and $\frac{1.8}{63}$ (according to mole concepts)

Number of electrons required to discharge Ag and Cu will be proportional to charges.

Hence total charge is $\frac{1}{108}$ + $2\times \frac{1.8}{63}$.

All the charge is passed through 12V battery so total energy is = [$\frac{1}{108}$ + $2\times \frac{1.8}{63}$] $\times$ 12 $\times$[Avogadro number]

Therefore total energy is $4.34\times {10}^{4}J$