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Date May 2015 Marks available 1 Reference code 15M.1.hl.TZ2.16
Level HL Paper 1 Time zone TZ2
Command term Question number 16 Adapted from N/A

Question

Which equation represents the standard enthalpy change of formation, ΔHΘf, of tetrachloromethane?

A.     C(g)+4Cl(g)CCl4(g)

B.     C(s)+4Cl(g)CCl4(l)

C.     C(g)+2Cl2(g)CCl4(g)

D.     C(s)+2Cl2(g)CCl4(l)

Markscheme

D

Examiners report

It is accepted that candidates should not have come across tetrachloromethane, CCl4, it having been banned for many years. They were not expected to know that it is a liquid at room temperature and the question can be answered correctly without this knowledge. A standard enthalpy change of formation must start from the elements so only C and D are possible. Carbon is not a gas under standard conditions so answer C is excluded. Nearly 47% gave the correct answer.

Syllabus sections

Core » Topic 5: Energetics/thermochemistry » 5.1 Measuring energy changes
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