A student electrolyses a concentrated aqueous solution of one compound using graphite electrodes. The compound is one of these:

The table shows the student's observations.

Electrode	Observations
Negative electrode	Bubbles of a colourless gas form. The gas burns with a squeaky pop when a lit splint is held to it. No solid forms on the electrode.
Positive electrode	Bubbles of a pale green gas form. Damp blue litmus paper held near the electrode turns red and then white.

Identify the compound in the solution. Use the observations at both electrodes to justify your answer.

Deduce which ions are left in the solution after electrolysis. Explain your answer.

A student electrolyses a concentrated aqueous solution of one compound using graphite electrodes. The compound is one of these:

The table shows the student's observations.

Electrode	Observations
Negative electrode	Bubbles of a colourless gas form. The gas burns with a squeaky pop when a lit splint is held to it. No solid forms on the electrode.
Positive electrode	Bubbles of a pale green gas form. Damp blue litmus paper held near the electrode turns red and then white.

Identify the compound in the solution. Use the observations at both electrodes to justify your answer.

Deduce which ions are left in the solution after electrolysis. Explain your answer.

3.4 Electrolysis

3.4 Electrolysis Questions