Question

Kinetics.

Broadly speaking, the factors that influence chemical reaction rates may be summarised as follows.

Chemical nature of reactants (Is the chemical reaction thermodynamically “downhill” so that it can occur spontaneously at all?)

Reactant Concentration (or pressure for a gas)

Physical state of reactants (e.g. phase, or surface area of solids)

Presence of catalyst

Temperature

For each of the following observations, identify which one these five factors is most important, and briefly explain how/why that is the case.

(a) The ability to sustain aerobic exercise is limited by the amount of haemoglobin in the blood.

(b) Non-starch polysaccharides are large complex carbohydrates, and an important source of fibre. Their chemical energy content is similar to other carbohydrates like sucrose, but they do not undergo respiration via by human digestion. Why not?

(c) Potato is made edible by cooking it.

(d) Digestion is enhanced by chewing our food.

Answer 1

Chemical reactions

Factors affecting the following reactions,

(a) The ability to sustain aerobic exercise is limited by the amount of haemoglobin in the blood : Reactant (Haemoglobin) concentration.

(b) Non-starch polysaccharides are large complex carbohydrates, and an important source of fibre. Their chemical energy content is similar to other carbohydrates like sucrose, but they do not undergo respiration via by human digestion : Chemical nature of reactant. As non-starch polysccarides do not break into smaller units easily, they cannot undergo respiration via human digestion.

(c) Potato is made edible by cooking it : Temperature.

(d) Digestion is enhanced by chewing our food : Presence of catalyst. The catalyst present in saliva help digest food when chewing.