DP Chemistry (first assessment 2025)
Question 19M.2.HL.TZ1.4b(ii)
| Date | May 2019 | Marks available | [Maximum mark: 2] | Reference code | 19M.2.HL.TZ1.4b(ii) |
| Level | HL | Paper | 2 | Time zone | TZ1 |
| Command term | Determine | Question number | b(ii) | Adapted from | N/A |
b(ii).
[Maximum mark: 2]
19M.2.HL.TZ1.4b(ii)
(b(ii))
Two more trials (2 and 3) were carried out. The results are given below.
Determine the rate equation for the reaction and its overall order, using your answer from (b)(i).
Rate equation:
Overall order:
[2]
Markscheme
Rate equation:
Rate = k[H2O2] × [KI] [✔]
Overall order:
2 [✔]
Note: Rate constant must be included.
Examiners report
Good performance but with answers that either typically included only [H2O2] with first or second order equation or even suggesting zero order rate equation.
Syllabus sections
Reactivity 2. How much, how fast and how far? » Reactivity 2.2—How fast? The rate of chemical change » Reactivity 2.2.10—The order of a reaction with respect to a reactant is the exponent to which the concentration of the reactant is raised in the rate equation. The order with respect to a reactant can describe the number of particles taking part in the rate determining step. The overall reaction order is the sum of the orders with respect to each reactant. Sketch, identify and analyse graphical representations of zero, first and second order reactions.