Question

The negative Zn pole of a Daniel cell, sending a constant current through a circuit, decreases in mass by 0.13g in 30 minutes. If the electrochemical equivalent of Zn and Cu are 32.5 and 31.5 respectively, the increase in the mass of the positive Cu pole in this time is

• A. 0.242 g
• B. 0.190 g
• C. 0.141 g
• D. 0.126 g

Answer 1

Answer: (D)

0.126 g

Answer 2

$m = Zit$ ⇒ $\frac{m_{Cu}}{m_{Zn}} = \frac{Z_{Cu}}{Z_{Zn}}$

$m_{Cu} = m_{Zn}\frac{Z_{Cu}}{Z_{Zn}} = 0.13 \times \frac{31.5}{32.5} = 0.126g$