DP Chemistry (first assessment 2025)
Question 19M.1A.SL.TZ2.16
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.1A.SL.TZ2.16 |
| Level | SL | Paper | 1A | Time zone | TZ2 |
| Command term | Question number | 16 | Adapted from | N/A |
16.
[Maximum mark: 1]
19M.1A.SL.TZ2.16
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)
[1]
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
Structure 2. Models of bonding and structure » Structure 2.1—The ionic model » Structure 2.1.3—Ionic compounds exist as three-dimensional lattice structures, represented by empirical formulas. Explain the physical properties of ionic compounds to include volatility, electrical conductivity and solubility.