DP Chemistry (first assessment 2025)
Question 22N.1A.HL.TZ0.30
| Date | November 2022 | Marks available | [Maximum mark: 1] | Reference code | 22N.1A.HL.TZ0.30 |
| Level | HL | Paper | 1A | Time zone | TZ0 |
| Command term | Solve | Question number | 30 | Adapted from | N/A |
30.
[Maximum mark: 1]
22N.1A.HL.TZ0.30
The standard electrode potentials for three half-cells involving chromium are shown.
Cr3+ (aq) + e− Cr2+ (aq) E⦵ = −0.407 V
Cr3+ (aq) + 3e− Cr (s) E⦵ = −0.744 V
Cr2+ (aq) + 2e− Cr (s) E⦵ = −0.914 V
Which statement is correct?
A. Cr3+ (aq) can oxidize Cr2+ (aq) but not Cr (s).
B. Cr3+ (aq) can oxidize Cr (s) but not Cr2+ (aq).
C. Cr3+ (aq) can oxidize both Cr2+ (aq) and Cr (s).
D. Cr3+ (aq) can oxidize Cr (s) and reduce Cr2+ (aq).
[1]
Markscheme
B
Examiners report
A poorly answered question with only 33% of candidates being able to deduce the relative strengths of oxidizing and reducing agents based on standard electrode potential data. All distractors were quite effective, indicating significant confusion.
Syllabus sections
Reactivity 3. What are the mechanisms of chemical change? » Reactivity 3.2—Electron transfer reactions » Reactivity 3.2.12—The hydrogen half-cell H+(aq) + e− ⇌12 H2(g) is assigned a standard electrode potential of zero by convention. It is used in the measurement of standard electrode potential, E⦵. Interpret standard electrode potential data in terms of ease of oxidation/reduction.