Electrochemical equivalents are constants used in electrolysis calculations. They are essentially the amount of substance (in grams) that will be deposited or dissolved by the electrochemical equivalent of a given current over a certain period of time. The value for electrochemical equivalents depends on the substance being considered.
Here's how you can calculate it for different substances:
1. **For Metals**: The electrochemical equivalent (E) can be calculated using the formula:
\[
E = \frac{M}{n \cdot F}
\]
where:
- \( M \) is the molar mass of the metal (in grams per mole),
- \( n \) is the number of electrons involved in the electrochemical reaction,
- \( F \) is Faraday’s constant (approximately \( 96485 \, \text{C/mol} \)).
2. **For Water Electrolysis**: The electrochemical equivalent for water electrolysis is commonly used and is approximately:
- For the production of hydrogen: \( 0.000091 \, \text{g/C} \) (grams per Coulomb),
- For the production of oxygen: \( 0.000091 \, \text{g/C} \) (grams per Coulomb), given the reactions involved.
### Examples:
- **Copper (Cu)**: The molar mass of copper is \( 63.55 \, \text{g/mol} \), and it typically involves 2 electrons for deposition (Cu²⁺ + 2e⁻ → Cu). Thus, the electrochemical equivalent of copper is:
\[
E = \frac{63.55}{2 \cdot 96485} \approx 0.000658 \, \text{g/C}
\]
- **Zinc (Zn)**: The molar mass of zinc is \( 65.38 \, \text{g/mol} \), and it involves 2 electrons for deposition (Zn²⁺ + 2e⁻ → Zn). Thus, the electrochemical equivalent of zinc is:
\[
E = \frac{65.38}{2 \cdot 96485} \approx 0.000678 \, \text{g/C}
\]
These values are crucial in electroplating, electrolysis, and other electrochemical processes.