DP Chemistry (last assessment 2024)

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Question 19M.3.hl.TZ1.21

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Date May 2019 Marks available [Maximum mark: 3] Reference code 19M.3.hl.TZ1.21
Level hl Paper 3 Time zone TZ1
Command term Formulate, Outline Question number 21 Adapted from N/A
21.
[Maximum mark: 3]
19M.3.hl.TZ1.21

Mild heartburn is treated with antacids such as calcium carbonate.

(a)

Formulate an equation for the neutralization of stomach acid with calcium carbonate, CaCO3 (s).

[1]

Markscheme

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

 

Note: Accept balanced ionic equations involving “H+” or “H3O+”.

Do not accept “H2CO3”.

Examiners report

Responses were mixed with some candidates easily writing an equation for the neutralization of stomach acid with CaCO3. Others failed to score for having incorrect products such as H2CO3 or CaCl, or for using sulfuric acid instead of hydrochloric for stomach acid.

(b)

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:

[2]

Markscheme

Omeprazole:
inhibits enzyme/«gastric» proton pump «which secretes H+ ions into gastric juice»
OR
 inhibits the H+/K+-ATPase system   [✔]


Ranitidine:
inhibits/blocks H2/histamine receptors «in cells of stomach lining»
OR
prevents histamine binding to H2/histamine receptors «and triggering acid secretion»  [✔]

 

Note: Accept “H2-receptor antagonist” for M2.

Examiners report

Many candidates correctly outlined how drugs such as omeprazole and ranitidine regulate acid secretion.

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