\(6.6 \times 10^{-4}\)
The total charge passed is \( Q = I \times t = 0.5 \, \text{A} \times 3600 \, \text{s} = 1800 \, \text{C} \). The electrochemical equivalent \( k \) is given by \( k = \frac{\text{mass deposited}}{\text{charge passed}} = \frac{0.592}{1800} \approx 3.3 \times 10^{-4} \, \text{g/C} \).