Describe how mild analgesics function.

(i)     Outline why this substance is more soluble than standard aspirin in water.

(ii)     Deduce the balanced ionic equation for the reaction that occurs between soluble aspirin and the acid in the stomach.

(i)     Deduce two named functional groups present in both aspirin and diamorphine.

(ii)     Deduce one named functional group present in morphine but not in diamorphine.

(iii)     State two short-term advantages and two long-term disadvantages of using codeine as a strong analgesic.

Short-term advantages:

Long-term disadvantages:

intercepts pain stimulus at source / inhibits release of substances/prostaglandins that cause pain/swelling/fever;

(i)     ionic compound (which dissociates);

(ii)     \({{\text{C}}_9}{{\text{H}}_7}{\text{O}}_4^ - {\text{(aq)}} + {{\text{H}}^ + }{\text{(aq)}} \to {{\text{C}}_9}{{\text{H}}_8}{{\text{O}}_4}{\text{(aq)}}\);

Ignore state symbols

Ignore arrow.

(i)     phenyl/benzene ring;

Do not allow just benzene or arene or the formula C₆H₆.

ester;

Do not allow –COO– or carbonyl/CO.

(ii)     hydroxyl / phenol;

Allow alcohol/hydroxy but not hydroxide.

Do not allow –OH.

(iii)     Award [1] for any two short-term advantages from:

strong/powerful (pain reliever);

fast-acting / effective;

has a wide safety margin;

can quickly stop diarrhoea;

can be used in cough mixtures/medicines / antitussive properties;

works effectively with paracetamol/acetaminophen;

Award [1] for any two long-term disadvantages from:

(regular use) can lead to addiction/dependence/withdrawal symptoms;

tolerance can lead to toxic dosages;

can result in depression / apathy;

can cause mental health problems;

can result in constipation;

can result in sterility/sexually related problems;

memory loss;

serious health risk to babies who are breastfed;

Award [1 max] for one correct advantage and one correct disadvantage.

While many candidates scored the mark, some candidates offered vague and/or inaccurate descriptions of how mild analgesics functioned.

(i)     Few candidates scored here. Very often the answers would attribute the solubility to the presence of calcium.

(ii)     A highly discriminating question. A substantial number of candidates ignored the request for an ionic equation. Those who attempted one mostly failed to give the correct products.

(i)     Many correct answers. A few candidates stated “benzene” without “ring” which did not score the mark. Another mistake was using “esther” where it was not clear if “ester” or “ether” was meant.

(ii)     A well answered question.

(iii)     A good number of candidates scored at least one mark, often as a result of stating one short-term and one long-term advantage of using codeine.