Question 20N.3.HL.TZ0.3b.i
| Date | November 2020 | Marks available | [Maximum mark: 1] | Reference code | 20N.3.HL.TZ0.3b.i |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Predict | Question number | b.i | Adapted from | N/A |
Sodium alginate beads were prepared containing a suspension of Chlorella algae. These beads were placed in nine small jars containing hydrogencarbonate indicator solution. Hydrogencarbonate indicator is commonly used to detect changes in pH.
The jars were placed at different distances from a lamp, which was the only light source. The distances ranged from 40 to 130 centimetres. Jars were placed one at a time to avoid the jars from shading each other. Colour changes were observed.
[Source: © International Baccalaureate Organization 2020.]
The colours of the indicator in the jars ranged from yellow to purple after five hours.
Predict the distribution of indicator colours in jars 1 to 9.
[1]
the jars closer to the light had more purple colours
OR
the jar the furthest from the light was yellow
OR
purple to yellow
Allow for answers indicating colours for each jar within this range.
Most candidates predicted the colour range accurately from purple to yellow; weaker candidates either inverted the range or did not include the extremes (e.g. purple to magenta), which were stated in the question stem.
