Question 17N.3.sl.TZ0.9
| Date | November 2017 | Marks available | [Maximum mark: 5] | Reference code | 17N.3.sl.TZ0.9 |
| Level | sl | Paper | 3 | Time zone | TZ0 |
| Command term | Describe, Draw, Explain | Question number | 9 | Adapted from | N/A |
Lactose is a disaccharide formed by the condensation reaction of the monosaccharides galactose and glucose.
Describe what is meant by a condensation reaction.
[2]
«reaction in which» two reactants/molecules/functional groups bond/react «to form a larger molecule/single main product»
small/tiny molecule
OR
H2O formed
Accept formula or name of a specified small molecule other than water such as ammonia, ethanoic/acetic acid,
ethanol, hydrogen sulfide etc. for M2.
Do not accept just “molecule formed”.
Award [1 max] for an example giving an equation of a condensation reaction such as the formation of a disaccharide.
Draw the structure of galactose on the skeleton provided.
[1]
Accept “alpha” or “beta” form of galactose.
Explain how the inclusion of carbohydrates in plastics makes them biodegradable.
[2]
Any two of:
makes the plastic more hydrophilic/water soluble
carbohydrates are broken down/hydrolysed by bacteria/microorganisms
makes plastic more accessible to bacteria as holes/channels are created
OR
plastic of lower density is more permeable/susceptible to water/oxygen/heat/pressure
weakens intermolecular/London/dispersion/instantaneous induced dipole-induced dipole forces «between polymer chains in the plastic»
Accept “van der Waals/vdW” for “London” forces.
[Max 2 Marks]