Question 21M.2.SL.TZ1.6
| Date | May 2021 | Marks available | [Maximum mark: 5] | Reference code | 21M.2.SL.TZ1.6 |
| Level | SL | Paper | 2 | Time zone | TZ1 |
| Command term | Deduce, Draw, Outline, Suggest | Question number | 6 | Adapted from | N/A |
When dinitrogen pentoxide, N2O5, is heated the colourless gas undergoes thermal decomposition to produce brown nitrogen dioxide:
N2O5 (g) → 2NO2 (g) + O2 (g)
Data for the decomposition at constant temperature is given.
Suggest how the extent of decomposition could be measured.
[1]
use colorimeter
OR
change in colour
OR
change in volume
OR
change in pressure ✔
Accept suitable instruments, e.g. pressure probe/oxygen sensor.
Plot the missing point on the graph and draw the best-fit line.
[2]
point correct ✔
straight line passing close to all points AND through origin ✔
Accept free hand drawn line as long as attempt to be linear and meets criteria for M2.
Deduce the relationship between the concentration of N2O5 and the rate of reaction.
[1]
« rate of reaction is directly» proportional to/∝[N2O5]
OR
doubling concentration doubles rate ✔
Do not accept “rate increases as concentration increases”/ positive correlation
Accept linear
Outline why increasing the concentration of N2O5 increases the rate of reaction.
[1]
greater frequency of collisions «as concentration increases»
OR
more collisions per unit time «as concentration increases» ✔
Accept “rate/chance/probability/likelihood” instead of “frequency”.
Do not accept just “more collisions”.