Question

If 5 amperes of current is passed for 193 seconds through a solution containing copper salt, \(0.32\ g\) of copper is deposited. What is the oxidation state of Cu in the salt?

• A. \(+2\)
• B. \(+1\)
• C. \(+3\)
• D. \(+\dfrac{3}{2}\)

Hint:

In electrolysis, \[ Q=It \] and \[ 1\ \text{Faraday}=96500\ C \] Always calculate the moles of electrons first and then relate them to the electrode reaction to determine the oxidation state.

Answer 1

The Correct Option is A

Step 1: Use the equivalent weight form of Faraday's law directly.
\[ E=\frac{m\times96500}{I\times t} \]

Step 2: Substitute the values.
\[ E=\frac{0.32\times96500}{5\times193}=\frac{0.32\times96500}{965} \]

Step 3: Simplify.
Since $\dfrac{96500}{965}=100$,
\[ E=0.32\times100=32 \]

Step 4: Find the oxidation state from atomic mass over equivalent weight.
\[ n=\frac{\text{Atomic Mass}}{E}=\frac{64}{32}=2 \]
\[ \boxed{+2} \]
which is option (1).