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Copper of 0.2g and silver of 1.2g are deposited when current is passed through copper...

Physics
JAMB 2025

Copper of 0.2g and silver of 1.2g are deposited when current is passed through copper and silver voltameter. Calculate the electrochemical equivalent, Z of silver if that of copper is 0.00028gC\(^{-1}\)

  • A. 1.68 x 10\(^{-3}\)gC\(^{-1}\)
  • B. 2.34 x 10\(^{-3}\)gC\(^{-1}\)
  • C. 2.80 x 10\(^{-3}\)gC\(^{-1}\)
  • D. 3.34 x 10\(^{-3}\)gC\(^{-1}\)
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Correct Answer: Option A
Explanation

From Faraday's first law, the mass deposited \( m = Z Q \), where \( Z \) is the electrochemical equivalent and \( Q \) is the charge passed.

Since the same charge \( Q \) passes through both voltmeters:  
\(Q = \frac{m_{\mathrm{Cu}}}{Z_{\mathrm{Cu}}} = \frac{m_{\mathrm{Ag}}}{Z_{\mathrm{Ag}}} \)

Rearranging for \( Z_{\mathrm{Ag}} \):  
\(Z_{\mathrm{Ag}} = \frac{m_{\mathrm{Ag}} \cdot Z_{\mathrm{Cu}}}{m_{\mathrm{Cu}}} \)

But:  \( m_{\mathrm{Cu}} = 0.2 \, \mathrm{g} \), \( m_{\mathrm{Ag}} = 1.2 \, \mathrm{g} \),  \( Z_{\mathrm{Cu}} = 0.00028 \, \mathrm{g \, C^{-1}} \)  

\(Z_{\mathrm{Ag}} = \frac{1.2 \times 0.00028}{0.2} = \frac{0.000336}{0.2} = 0.00168 \, \mathrm{g \, C^{-1}} \)

There is an explanation video available below.


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Explanation Video

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Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts