DP Chemistry (last assessment 2024)
Question 19M.2.hl.TZ2.d(iv)
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.2.hl.TZ2.d(iv) |
| Level | hl | Paper | 2 | Time zone | TZ2 |
| Command term | Calculate | Question number | d(iv) | Adapted from | N/A |
d(iv).
[Maximum mark: 1]
19M.2.hl.TZ2.d(iv)
Carbonated water is produced when carbon dioxide is dissolved in water under pressure. The following equilibria are established.
Equilibrium (1) CO2 (g) 
CO2 (aq)
Equilibrium (2) CO2 (aq) + H2O (l) 
H+ (aq) + HCO3− (aq)
Soda water has sodium hydrogencarbonate, NaHCO3, dissolved in the carbonated water.
The uncertainty of the 100.0cm3 volumetric flask used to make the solution was ±0.6cm3.
Calculate the maximum percentage uncertainty in the mass of NaHCO3 so that the concentration of the solution is correct to ±1.0 %.
[1]
Markscheme
«1.0 – 0.6 = ± » 0.4 «%» [✔]
Examiners report
Mixed responses, more attention should be given to this simple calculation which is straightforward and should be easy as required for IA reports.
