| Date | May 2016 | Marks available | 3 | Reference code | 16M.3.sl.TZ0.18 |
| Level | SL | Paper | 3 | Time zone | TZ0 |
| Command term | Compare and contrast | Question number | 18 | Adapted from | N/A |
Question
Magnesium hydroxide is the active ingredient in a common antacid.
Formulate the equation for the neutralization of stomach acid with magnesium hydroxide.
Determine the mass of HCl, in g, that can be neutralized by the standard adult dose of 1.00g magnesium hydroxide.
Compare and contrast the use of omeprazole (Prilosec) and magnesium hydroxide.
Markscheme
Mg (OH)2(s) + 2HCl (aq) → 2H2O (l) + MgCl2 (aq)
OR
Mg (OH)2 (s) + 2H+ (aq) → Mg2+ (aq) + 2H2O (l)
\(\frac{{1.00}}{{58.33}}\)=0.0171«molMg(OH)2»
«0.0171×2×36.46=»1.25«g»
Award [2] for 1.25 or 1.26 «g».
Award [1 max] for any similarity:
both compounds relieve symptoms of acid reflux/heartburn/indigestion
OR
both increase the stomach pH
both cause diarrhoea
Award [2 max] for any two differences:
omeprazole stops the production of acid/is a proton-pump inhibitor AND magnesium hydroxide neutralizes the «excess» acid that is present
omeprazole takes longer «than magnesium hydroxide» to provide relief
omeprazole is used to treat ulcers while magnesium hydroxide is not
omeprazole can prevent long term damage from overproduction of acid AND magnesium hydroxide does not
OR
omeprazole has a long term effect AND magnesium hydroxide has a short-term effect «only»
magnesium hydroxide affects ionic balance in the body AND omeprazole does not
Award [1 max] if two or three correct points are given about one of the compounds without addressing the other compound.
