Transferred errors

This term is used by examiners to indicate that a mark has been awarded because the method was correct despite the answer being wrong. This happens because of an earlier mistake in the calculation, but you should not be penalized twice for the same mistake. It will usually be indicated on your script as TE (transferred error) or ECF (error carried forward).

Transferred errors benefit students who clearly show their working. A correct answer with no working will generally be awarded full marks. However, one small error will give an incorrect final answer. An incorrect final answer with no working will gain no credit. If you show your working you will only lose one mark for the error, even though the final answer (and maybe all the intermediate answers) is wrong.

It is always worth carrying on with a calculation if you know the method. If you are unsure about how to get an answer early in the calculation just take a guess (preferably an educated guess!) at this part of the calculation.

Example

In an iodine-thiosulfate titration 17.6 cm³ of 0.100 M sodium thiosulfate solution was used. The student first calculates the number of moles of sodium thiosulfate incorrectly by forgetting to convert the volume into dm³:

Number of moles of sodium thiosulfate = 0.100 × 17.6 = 1.76 mol

This gains no marks. The correct equation is given and gains a mark:

2Na₂S₂O₃(aq) + I₂(aq) ⇒ Na₂S₄O₆(aq) + 2NaI(aq)

The link between the number of moles of sodium thiosulfate and iodine is now made:

\ Number of moles of iodine = ½ × 1.76 = 0.88 mol

Although the answer of 0.88 mol is wrong (and ridiculously big!), it is still awarded a mark because the candidate correctly understood the method of using the equation to work out the number of moles of the other substance.