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Date May 2019 Marks available 1 Reference code 19M.1.hl.TZ2.16
Level HL Paper 1 Time zone TZ2
Command term Question number 16 Adapted from N/A

Question

Which equation represents lattice enthalpy?

A. NaCl (g) → Na+ (g) + Cl (g)

B. NaCl (s) → Na+ (g) + Cl (g)

C. NaCl (s) → Na+ (aq) + Cl (aq)

D. NaCl (s) → Na+ (s) + Cl (s)

Markscheme

B

Examiners report

72 % of candidates chose the correct equation that represents lattice enthalpy. Many candidates chose A, where the ionic compound (NaCl) was gaseous, and others chose distractor C, where the ions produced were aqueous. The discrimination index for the question was quite high.

Syllabus sections

Additional higher level (AHL) » Topic 15: Energetics/thermochemistry » 15.1 Energy cycles
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