DP Chemistry (first assessment 2025)
Question 22N.1A.SL.TZ0.17
| Date | November 2022 | Marks available | [Maximum mark: 1] | Reference code | 22N.1A.SL.TZ0.17 |
| Level | SL | Paper | 1A | Time zone | TZ0 |
| Command term | Determine | Question number | 17 | Adapted from | N/A |
17.
[Maximum mark: 1]
22N.1A.SL.TZ0.17
Which changes would increase the rate of an exothermic reaction?
[1]
Markscheme
A
Examiners report
This question had a poor discrimination index as it appears to have confused the high-scoring candidates. Half of the candidates selected an increase in temperature and a decrease in particle size to increase the rate of an exothermic reaction. The most commonly chosen distractor was a decrease in temperature and particle size.
Syllabus sections
Reactivity 2. How much, how fast and how far? » Reactivity 2.2—How fast? The rate of chemical change » Reactivity 2.2.3—Factors that influence the rate of a reaction include pressure, concentration, surface area, temperature and the presence of a catalyst. Predict and explain the effects of changing conditions on the rate of a reaction.
Reactivity 1. What drives chemical reactions? » Reactivity 1.4—Entropy and spontaneity (Additional higher level) » Reactivity 1.4.1—Entropy, S, is a measure of the dispersal or distribution of matter and/or energy in a system. The more ways the energy can be distributed, the higher the entropy. Under the same conditions, the entropy of a gas is greater than that of a liquid, which in turn is greater than that of a solid. Predict whether a physical or chemical change will result in an increase or decrease in entropy of a system. Calculate standard entropy changes, ΔS⦵, from standard entropy values, S⦵.
Reactivity 1. What drives chemical reactions? » Reactivity 1.4—Entropy and spontaneity (Additional higher level) » Reactivity 1.4.2—Change in Gibbs energy, ΔG, relates the energy that can be obtained from a chemical reaction to the change in enthalpy, ΔH, change in entropy, ΔS, and absolute temperature, T. Apply the equation ΔG⦵ = ΔH⦵ − TΔS⦵ to calculate unknown values of these terms.