Question 19M.2.hl.TZ1.e
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.hl.TZ1.e |
| Level | hl | Paper | 2 | Time zone | TZ1 |
| Command term | Explain | Question number | e | Adapted from | N/A |
This question is about iron.
An iron nail and a copper nail are inserted into a lemon.
Explain why a potential is detected when the nails are connected through a voltmeter.
[2]
lemon juice is the electrolyte
OR
lemon juice allows flow of ions
OR
each nail/metal forms a half-cell with the lemon juice [✔]
Any one of:
iron is higher than copper in the activity series
OR
each half-cell/metal has a different redox/electrode potential [✔]
iron is oxidized
OR
Fe → Fe2+ + 2e−
OR
Fe → Fe3+ + 3e−
OR
iron is anode/negative electrode of cell [✔]
copper is cathode/positive electrode of cell
OR
reduction occurs at the cathode
OR
2H+ + 2e− → H2 [✔]
electrons flow from iron to copper [✔]
Very few candidates scored M1 regarding the lemon juice role as electrolyte. Some earned M2 but a lot of answers were too vague, such as ‘electrons move through the circuit’, etc.
