Zadanie 3e, Paper 1B, listopad 2025, TZ1, Chemia IB HL
Wzorowane na: Chemistry HL Paper 1B, November 2025, TZ1, pytanie 3(e). Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
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Zadanie
Wspólne informacje do wiązki zadań
A student used paper chromatography to find out which coloured dyes had been mixed to make the brown ink of a marker pen, and to compare the polarities of those dyes. A spot of the ink was placed on the start line of each of two identical paper strips. The start line was drawn in pencil 1.5 cm from the bottom edge of the strip, and each strip was placed in a covered beaker containing a different solvent system, both mixtures of ethanol and water. System 1 was 25 % ethanol and 75 % water by volume; system 2 was 75 % ethanol and 25 % water by volume. Each run gave four coloured spots. The positions of the start line, the solvent front and the spots were measured from the bottom edge of each strip.
| Position measured from the bottom edge / cm | System 1 (25 % ethanol) | System 2 (75 % ethanol) |
|---|---|---|
| Start line | 1.5 | 1.5 |
| Solvent front | 17.5 | 15.5 |
| Violet spot | 16.2 | 5.6 |
| Blue spot | 14.1 | 11.3 |
| Orange spot | 11.1 | 7.8 |
| Yellow spot | 3.3 | 3.0 |
PowiększPolecenie
The student suspected that the ink contained more than four dyes, and that one of the spots was two dyes that had not separated.
Suggest how the student could modify the chromatography experiment to test this idea.
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Pokaż rozwiązanieUkryj rozwiązanieKlucz i punktacja
Odpowiedź z klucza
Any one of:
use a different solvent «system» ✔
run two-way chromatography: turn the paper through 90° AND run it again in a second solvent ✔
use a longer strip of paper «and run it for longer» ✔
use thin-layer chromatography «silica gel plate» instead of paper ✔
Schemat punktowania
[1 max] for any one modification. 'Repeat the experiment' or 'use more ink' earns nothing.