Question 20N.1B.SL.TZ0.b
| Date | November 2020 | Marks available | [Maximum mark: 2] | Reference code | 20N.1B.SL.TZ0.b |
| Level | SL | Paper | 1B | Time zone | TZ0 |
| Command term | Explain | Question number | b | Adapted from | N/A |
The ice bath is used at equilibrium to slow down the forward and reverse reactions. Explain why adding a large amount of water to the reaction mixture would also slow down both reactions.
[2]
dilution/lower concentrations ✔
less frequent collisions «per unit volume» ✔
Accept “lowers concentration of acid catalyst” for M1. M2 must refer to increase in activation energy or different pathway.
Do not accept responses referring to equilibrium.
A significant number of students scored at least one mark, usually the first and many both. Weaker students lost the second mark by referring to less collisions instead of less frequent collision or other words to this effect. Very few students referred to more diluted catalyst and of those even less were able to provide an adequate explanation in terms of the increased Ea. Many students tried to answer this question in terms of equilibrium instead of kinetics. There were also several responses that replied as if the dilution would only occur for part of the reaction or individual reactants instead of the entire solution.
