Question

What is the mass ratio of the gases collected at the anode and cathode?

Answer 1

Step 1: Understand the context – Electrolysis of water:
During the electrolysis of water, water (H₂O) is broken down into hydrogen and oxygen gases.
- Hydrogen gas (H₂) is collected at the cathode.
- Oxygen gas (O₂) is collected at the anode.

Step 2: Mole ratio from the reaction:
The balanced chemical equation is:
\[ 2H_2O \rightarrow 2H_2 + O_2 \]
This shows:
- 2 moles of hydrogen gas (H₂) are produced
- 1 mole of oxygen gas (O₂) is produced

Step 3: Calculate molar masses:
- Molar mass of H₂ = 2 g/mol
- Molar mass of O₂ = 32 g/mol

Step 4: Calculate mass ratio:
From the equation:
- 2 moles of H₂ = 2 × 2 = 4 g
- 1 mole of O₂ = 32 g

Therefore, the mass ratio of hydrogen to oxygen is:
\[ \text{Hydrogen : Oxygen} = 4 : 32 = 1 : 8 \]

Step 5: Conclusion:
The mass ratio of the gases collected at the cathode (H₂) and anode (O₂) is 1 : 8.