| 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)+2HCl(aq)«→MgCl2(aq)+2H2O(l)» AND
CaCO3(s)+2HCl(aq)«→CaCl2(aq)+H2O(l)+CO2(g)» ✔
Mg𝑛(OH)2=«0.20058.32=»3.43×10−3«mol» AND
CaCO3𝑛=«0.220100.09=»2.20×10−3«mol» ✔
«tablet of» X neutralizes 6.86×10−3«mol» HCl AND «tablet of» Y neutralizes 4.40×10−3«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
- 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
