IB Questionbank

User interface language: English | Español

Date	November 2020	Marks available	3	Reference code	20N.3.sl.TZ0.12
Level	SL	Paper	3	Time zone	TZ0
Command term	Show	Question number	12	Adapted from	N/A

Question

Consider the following antacids:

Show that antacid X is more effective, per tablet, than antacid Y.

Markscheme

same reactant mole ratio «in both equations»
OR
$Mg (OH)_{2} (s) + 2 HCl (aq) « \to {MgCl}_{2} (aq) + 2 H_{2} O (l) »$ AND
${CaCO}_{3} (s) + 2 HCl (aq) « \to {CaCl}_{2} (aq) + H_{2} O (l) + {CO}_{2} (g) »$ ✔

${}_{𝑛}{Mg} (OH)_{2} = « \frac{0.200}{58.32} = » 3.43 \times 10^{- 3} « mol »$ AND
${}_{𝑛}{CaCO}_{3} = « \frac{0.220}{100.09} = » 2.20 \times 10^{- 3} « mol »$ ✔

«tablet of» X neutralizes $6.86 \times 10^{- 3} « mol » HCl$ AND «tablet of» Y neutralizes $4.40 \times 10^{- 3} « mol » HCl$ ✔

Award [3] for correct final statement AND values in M3.

Examiners report

Very poorly answered. Many students scored at least 1 point. This was usually M2 by determining the mols
of each antacid present. However, many students totally ignored the corresponding balanced chemical equations or entered wrong ones. A worrying number of candidates didn't therefore use the correct molar ratio to calculate the values in M3. Showing the calculations and how X is more effective than Y was the point of the question.

Syllabus sections

Options » D: Medicinal chemistry » D.1 Pharmaceutical products and drug action

17N.3.sl.TZ0.18b: State the method of drug administration that gives the maximum bioavailability.
17M.3.sl.TZ2.15b.ii:
Compare, giving a reason, the bioavailability of soluble aspirin with aspirin.
18N.3.sl.TZ0.12a: State the internal bond angles in the β-lactam ring and the expected bond angles for the same...
18N.3.sl.TZ0.13c: Outline the meaning of the bioavailability of a drug.
18N.3.hl.TZ0.17b: Outline the meaning of the bioavailability of a drug.
18M.3.sl.TZ2.15:
Drug testing is necessary to determine safe and effective doses.

Distinguish between the lethal dose (LD₅₀) and the toxic dose (TD₅₀).
19M.3.hl.TZ1.22b:
Suggest a reason for using a phosphate salt of oseltamivir in oral tablets.
19M.3.sl.TZ1.17a(ii):
Suggest a reason for using a phosphate salt of oseltamivir in oral tablets.
17M.3.sl.TZ2.18b:
Suggest one ethical consideration faced by medical researchers when developing medications.
19N.3.hl.TZ0.21b: Experimental research on both animals and humans contributes to the development...
18M.3.sl.TZ1.13b.i:
State what is meant by the bioavailability of a drug.
19M.3.hl.TZ2.21a:
Distinguish between therapeutic window and therapeutic index in humans.

Therapeutic window:

Therapeutic index:
17N.3.sl.TZ0.18a:
Outline the difference between the therapeutic index in animal studies and the therapeutic index in humans.
17M.3.sl.TZ1.18a:
Dose response curves are determined for each drug.

Outline the significance of range “a”.
19M.3.sl.TZ2.14a:
Distinguish between therapeutic window and therapeutic index in humans.

Therapeutic window:

Therapeutic index:
20N.3.sl.TZ0.11d:
Comment on the risk of overdose when taking aspirin as an analgesic, referring to the following values, for a person weighing $70 kg$ :

Minimum therapeutic dose $= 0.5 g$

Estimated minimum lethal dose $= 15 g$
20N.3.hl.TZ0.15d:
Comment on the risk of overdose when taking aspirin as an analgesic, referring to the following values, for a person weighing $70 kg$ :

Minimum therapeutic dose $= 0.5 g$

Estimated minimum lethal dose $= 15 g$

Core » Topic 1: Stoichiometric relationships » 1.2 The mole concept

Core » Topic 1: Stoichiometric relationships

Options » D: Medicinal chemistry

Core

Options

Question

Markscheme

Examiners report

Syllabus sections

View options