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					                     Emirates International School
                                                 Grade 13
                                   Drugs and medicines (Antacids)
Name:………………………………………………….                                                  Date:………………………………………

1. The normal pH of gastric juices is in the 1.0 – 3.0 range. State two purposes of this acidic solution

    and explain what causes heartburn.

    To suppress growth of harmful bacteria,

    and to help in digestion by hydrolysing proteins to amino acids.

    Heart burn is caused by stomach acid rising up the esophagus.

2. Describe what an antacid is made of and explain its purpose.

    An antacid is a base, usually, metal oxides, hydroxides, carbonates or hydrogen carbonates

    (bicarbonates) that neutralizes excess acid in the stomach to adjust the stomach pH to the desired

    level. It relieves indigestion and allows damage done by excess acid to the stomach lining to repair

    itself.…

3. Name four antacids each containing a different metal.

    sodium carbonate/sodium hydrogen carbonate; magnesium oxide/hydroxide; calcium carbonate,

    aluminium hydroxide…

4. For each antacid in (3) above, write a balanced chemical equation for its reaction with excess

    stomach acid.

    NaHCO3 (aq) + HCl (aq) →NaCl (aq) + H2O (l) + CO2 (g)

    Mg(OH)2 (aq) + 2HCl (aq) → MgCl2 (aq) +2 H2O (l)

    CaCO3 (s) + 2HCl (aq) → CaCl2 (aq) + H2O (l) + CO2 (g)

    Al(OH)3 (s) + 3 HCl (aq) → AlCl3 (aq) + 3 H2O (l) …
                    Emirates International School
                                               Grade 13
                                  Drugs and medicines (Antacids)
Name:………………………………………………….                                               Date:………………………………………

5. Explain why some antacids contain the chemical called dimethicone.

   Dimethicone is an anti-foaming agent that is added to some antacids to reduce the surface

   tension of gas bubbles, causing them to coalesce (come together) and prevents acid from rising up

   the oesophagus.…

6. Two solid antacid products containing the same mass of diἀerent active ingredients are on sale for

   the same price. One contains magnesium hydroxide, the other calcium carbonate as the active

   ingredient. Without detailed calculations, deduce which one is a better buy and explain your

   reasoning.

   Both ingredients neutralise 2 mol H+ per mol M(CaCO3) > M(Mg(OH)2)

   n = Mm; higher molar mass means less amount in moles of CaCO3;

   thus it will neutralise less H+ and Mg(OH)2 is a better buy.

				
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posted:10/11/2011
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