Question 20N.2.SL.TZ0.7a
| Date | November 2020 | Marks available | [Maximum mark: 3] | Reference code | 20N.2.SL.TZ0.7a |
| Level | SL | Paper | 2 | Time zone | TZ0 |
| Command term | Outline | Question number | a | Adapted from | N/A |
Outline how hydrogen bonds form in water.
[3]
a. water (molecules) are polar/dipolar/have partially positive and negative poles/have δ+ and δ-;
b. attraction/bonding between positive and negative (poles);
c. hydrogen bond formed between hydrogen and oxygen; Reject if H and O in same molecule.
d. bond/attraction between different water molecules/intermolecular;
Marks can be awarded in an annotated diagram.
Reject answers stating or implying that there are whole positive or negative charges for mpa.
Answers were mostly good here, with many candidates scoring full marks. A very common misconception was that hydrogen bonds are strong – a single hydrogen bond is a weak interaction and it is only because there are many hydrogen bonds in water that they collectively exert large cohesive forces. A few candidates thought that hydrogen bonds were within rather than between water molecules.
