This question is about electrolysis.
A student investigated the electrolysis of nickel chromate solution.
Nickel chromate solution is brownish-yellow. It contains:
- green coloured Ni2+\text{Ni}^{2+}Ni2+ ions
- yellow coloured CrO42−\text{CrO}_4^{2-}CrO42− ions
The apparatus used is shown below:
The student switched the power supply on and observed the changes at each electrode:
- Positive electrode (+): The solution turned yellow and bubbles of gas formed at the electrode.
- Negative electrode (-): The solution turned green and a solid formed on the electrode.
Explain why the solution turned yellow at the positive electrode.
The gas produced at the positive electrode was oxygen, which was produced from hydroxide ions. Name the substance in the solution that provides the hydroxide ions.
Describe, in terms of electrons, how the solid forms at the negative electrode. Include a balanced half-equation in your answer.
The student repeated the investigation using concentrated potassium bromide solution instead of nickel chromate solution. Name the product formed at each electrode.
- Negative electrode
- Positive electrode