| Date | May 2019 | Marks available | 1 | Reference code | 19M.3.hl.TZ2.23 |
| Level | HL | Paper | 3 | Time zone | TZ2 |
| Command term | Determine | Question number | 23 | Adapted from | N/A |
Question
Excess acid in the stomach can cause breakdown of the stomach lining.
Outline how ranitidine (Zantac) inhibits stomach acid production.
Outline two advantages of taking ranitidine instead of an antacid which neutralizes excess acid.
Some antacids contain carbonates.
Determine the pH of a buffer solution which contains 0.160 mol dm−3 CO32− and 0.200 mol dm−3 HCO3−, using section 1 of the data booklet.
pKa (HCO3−) = 10.32
Markscheme
blocks/binds H2/histamine receptors «in cells of stomach lining»
OR
prevents histamine molecules binding to H2/histamine receptors «and triggering acid secretion» [✔]
Any two of:
ranitidine can be effective in treating ulcers «but antacid is not» [✔]
ranitidine can prevent long-term damage «from overproduction of acid and antacid does not» [✔]
ranitidine has a long-term effect «and antacid has short-term effect only» [✔]
ranitidine does not affect ionic balance in body «and antacid does» [✔]
ranitidine does not produce bloating/flatulence [✔]
Note: Accept “ranitidine stops the over production of acid in the stomach while antacids neutralise the excess acid
giving temporary relief” for M2.
«pH = pKa »
«pH =»10.22 [✔]
Examiners report
Some candidates were not confident enough in their answers to receive a mark while others confused the action of ranitidine which blocks H2 receptors with omeprazole which is a proton pump inhibitor.
While most candidates were awarded at least one of the two marks possible for this question some of the descriptions were too vague or incomplete to receive a mark.
This was generally a well-answered question. Most candidates who did not receive the mark inverted the concentration of the conjugate base/concentration of the acid in the calculation.
Syllabus sections
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16N.3.sl.TZ0.19a:
Ranitidine (Zantac) is a drug that inhibits stomach acid production. Outline why the development of this drug was based on a detailed knowledge of the structure of histamine, shown below.
- 18N.3.sl.TZ0.14c: Suggest a technique for measuring the percentage mass of calcium carbonate in this type of...
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17N.3.sl.TZ0.20b:
The pH is maintained in different fluids in the body by the use of buffers.
Calculate the pH of a buffer solution of 0.0200 mol dm–3 carbonic acid, H2CO3, and 0.400 mol dm–3 sodium hydrogen carbonate, NaHCO3. The pKa of carbonic acid is 6.35.
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19M.3.hl.TZ2.23a(i):
Outline how ranitidine (Zantac) inhibits stomach acid production.
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17M.3.sl.TZ2.18a.i:
Compare and contrast the structures of oseltamivir and zanamivir, stating the names of functional groups.
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17N.3.sl.TZ0.20a:
Explain how ranitidine (Zantac) reduces stomach acid production.
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16N.3.sl.TZ0.19b:
Two other drugs, omeprazole (Prilosec) and esomeprazole (Nexium), directly prevent the release of acid into the stomach. Identify the site of action in the body.
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17M.3.hl.TZ2.22a:
Outline how ranitidine (Zantac) functions to reduce stomach acidity.
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18M.3.sl.TZ2.18b:
Calculate the amount, in mol, of stomach acid neutralized by an antacid tablet containing 0.750 g calcium carbonate.
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19N.3.sl.TZ0.16a:
Identify the compound responsible for the acidity of gastric juice, and state whether it is a strong or weak acid.
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18M.3.sl.TZ1.14b:
Explain how omeprazole (Prilosec) reduces stomach acidity.
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18N.3.sl.TZ0.14a:
Determine the pH of a buffer solution that is 0.0100 mol dm−3 sodium hydrogen carbonate and 0.0200 mol dm−3 sodium carbonate, using section 1 of the data booklet.
Ka (hydrogen carbonate ion) = 4.8 × 10−11
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17M.3.sl.TZ2.17a:
Two drugs are ranitidine (Zantac) and omeprazole (Prilosec). Outline how they function to reduce stomach acidity.
- 19N.3.sl.TZ0.16c: Outline how ranitidine reduces stomach acidity.
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19M.3.sl.TZ2.16a(ii):
Outline two advantages of taking ranitidine instead of an antacid which neutralizes excess acid.
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19N.3.sl.TZ0.16d:
Calculate the pH of a buffer solution which contains 0.20 mol dm−3 ethanoic acid and 0.50 mol dm−3 sodium ethanoate. Use section 1 of the data booklet.
pKa (ethanoic acid) = 4.76
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16N.3.sl.TZ0.19c:
A different approach to treating excess stomach acid is to neutralize it with antacids. Formulate an equation that shows the action of an antacid that can neutralize three moles of hydrogen ions, H+, per mole of antacid.
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19M.3.sl.TZ1.16a(ii):
Determine the volume of CO2 (g), in dm3, produced at STP, when 1.00 g of CaCO3 (s) reacts completely with stomach acid.
Mr CaCO3 = 100.09
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19M.3.sl.TZ2.16b:
Some antacids contain carbonates.
Determine the pH of a buffer solution which contains 0.160 mol dm−3 CO32− and 0.200 mol dm−3 HCO3−, using section 1 of the data booklet.
pKa (HCO3−) = 10.32
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18N.3.sl.TZ0.14b:
State the equation for the reaction of calcium carbonate, the active ingredient in some antacids, with stomach acid.
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18M.3.sl.TZ2.18a:
Formulate a chemical equation for the neutralization of stomach acid with calcium carbonate.
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18M.3.sl.TZ1.14a.ii:
Determine the amount, in mol, of hydrochloric acid neutralized by one antacid tablet.
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19N.3.sl.TZ0.16b:
An antacid contains calcium carbonate and magnesium carbonate.
Write the equation for the reaction of magnesium carbonate with excess stomach acid.
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19M.3.hl.TZ1.21a:
Formulate an equation for the neutralization of stomach acid with calcium carbonate, CaCO3 (s).
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17M.3.sl.TZ2.17b:
0.500 g of solid anhydrous sodium carbonate, Na2CO3(s), is dissolved in 75.0 cm3 of 0.100 moldm−3 sodium hydrogen carbonate solution, NaHCO3(aq). Assume the volume does not change when the salt dissolves.
HCO3−(aq) CO32−(aq) + H+(aq) pKa = 10.35.
Calculate the pH of the buffer solution.
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19M.3.hl.TZ2.23a(ii):
Outline two advantages of taking ranitidine instead of an antacid which neutralizes excess acid.
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18M.3.sl.TZ2.18c:
Explain how omeprazole (Prilosec) regulates pH in the stomach.
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19M.3.sl.TZ1.16a(i):
Formulate an equation for the neutralization of stomach acid with calcium carbonate, CaCO3 (s).
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17M.3.sl.TZ2.18a.ii:
Deduce the wavenumber of one absorbance seen in the IR spectrum of only one of the compounds, using section 26 of the data booklet.
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18M.3.sl.TZ1.14a.i:
An antacid tablet contains 680 mg of calcium carbonate, CaCO3, and 80 mg of magnesium carbonate, MgCO3.
State the equation for the reaction of magnesium carbonate with hydrochloric acid.
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17M.3.sl.TZ1.20a:
Calculate the pH of the buffer from the following data and section 1 of the data booklet.
pKa(CO2) = 6.34
[HCO3−(aq)] = 1.40 × 10−2 moldm−3
[CO2(aq)] = 1.25 × 10−3 moldm−3
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17M.3.sl.TZ1.20b:
Explain the effect of a large amount of aspirin on the pH of blood.
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19M.3.hl.TZ1.21b:
Acid secretion can be regulated by other types of drugs such as omeprazole and ranitidine. Outline how each of these drugs acts to reduce excess stomach acid.
Omeprazole:
Ranitidine:
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19M.3.sl.TZ2.16a(i):
Outline how ranitidine (Zantac) inhibits stomach acid production.
-
19M.3.sl.TZ1.16b:
Acid secretion can be regulated by other types of drugs such as omeprazole and ranitidine. Outline how each of these drugs acts to reduce excess stomach acid.
Omeprazole:
Ranitidine:
