Topic #2: Antacids
Medicine and Drugs unit 12
Terms in this set (17)
2) Two substances commonly used in antacid tablets are magnesium hydroxide and aluminium hydroxide.
a) State an equation to represent a neutralization reaction with one of the above antacids. (1)
Al(OH)3 + 3HCl → AlCl3 + 3H2O / Mg(OH)2 + 2HCl → MgCl2 + 2H2O
b) State and explain whether 0.1 mol of magnesium hydroxide is more effective or less effective than 0.1 mol of aluminium hydroxide. (1)
less effective and (magnesium hydroxide) 2/0.2 mol OH- ions available as compared to (aluminium hydroxide) 3/0.3 mol OH- ions for neutralization / neutralizes 2H+/0.2 mol acid as compared to 3H+/0.3 mol acid;
Do not accept aluminium hydroxide can neutralize more acid.
c) Suggest why compounds such as sodium hydroxide or potassium hydroxide cannot be used as an antacid. (1)
strong base / corrosive / harmful to the body;
d) Explain why alginates and dimethicone are often included in antacid tablets. (2)
provide a neutralizing layer on top of the stomach contents / to
prevent acid rising up the esophagus / prevents acid reflux/heartburn;
as an anti-foaming agent / to prevent flatulence/gas/bloating;
3) Sodium hydrogencarbonate, NaHCO3, and magnesium hydroxide, Mg(OH)2, can both be used as antacids.
a) Give the equations for the reactions of sodium hydrogencarbonate and magnesium hydroxide with hydrochloric acid. (2)
NaHCO3 + HCl → NaCl + H2O + CO2;
Accept H2CO3 instead of H2O and CO2.
Mg(OH)2 + 2HCl → MgCl2 + 2H2O;
b) Compare the effectiveness of 1.00 g of sodium hydrogencarbonate to 0.50 g of magnesium hydroxide in combating acidity in the stomach. (3)
Convert grams to moles:
n(NaHCO3) = 1.19 × 10-2 mol;
n(Mg(OH)2) = 8.57 × 10-3 mol;
Although there are more moles of NaHCO3, Mg(OH)2 reacts with twice the number of moles of acid , so it is more effective than NaHCO3 / OWTTE;
c) Explain why alginates are often added to antacids. (1)
produce a neutralizing layer/(foam) barrier which prevents heartburn/
acid rising into the esophagus;
4) Dyspepsia, commonly known as indigestion, is due to excess acid in the stomach and can be treated using antacids.
a) State the name of the acid found in the gastric juices of the stomach. (1)
Hydrochloric acid (do not accept HCl)
b) Two examples of antacids are aluminium hydroxide and calcium carbonate. State the equations to show the action of each antacid. (2)
Al(OH)3 + 3HCl → AlCl3 + 3H2O;
CaCO3 + 2HCl → CaCl2 + CO2 + H2O;
c) Antacid medicines often contain alginates and anti-foaming agents.
i) Explain briefly how alginates prevent heartburn. (2)
neutralizes excess stomach acid / produces neutralizing layer;
prevents acid in stomach from rising / prevents acid reflux;
ii) Explain why anti-foaming agents are added and state one example. (2)
prevent flatulence/(stomach) bloating / OWTTE;
dimethicone / polydimethylsiloxane/PDMS;
5) The walls of the human stomach contain cells that produce gastric juices. Sodium hydrogen carbonate is an antacid often used to neutralize excess acid.
a) State an equation for the reaction of stomach acid with this antacid. (1)
NaHCO3 + HCl → NaCl + H2O + CO2 / HCO3- + H+ → H2O + CO2;
States not required for mark.
b) Calcium carbonate can also neutralize stomach acid. The same amounts (in moles) of sodium hydrogen carbonate and calcium carbonate are available. Deduce which antacid will neutralize the greater amount of acid present in the stomach and explain your reasoning. (2)
1 mol NaHCO3 neutralizes 1 mol HCl and 1 mol CaCO3 neutralizes
2 mol HCl / CaCO3 + 2HCl → CaCl2 + H2O + CO2;
6) One common type of medicine taken orally is an antacid. Antacids such as sodium hydrogencarbonate are taken to reduce stomach acidity.
a) State the names of two metals, other than sodium, whose compounds are often used in antacids. (1)
magnesium / aluminium / calcium; (Any two for )
b) Write an equation for the neutralization of hydrochloric acid in the stomach by sodium hydrogencarbonate. (1)
NaHCO3 + HCl → NaCl + H2O + CO2; (Do not allow H2CO3)
c) Explain how heartburn is caused. (1)
acid from the stomach rises into the esophagus;
d) Explain why dimethicone is added to some antacids. (1)
as an anti-foaming agent / to prevent problem in (c) / to prevent flatulence;
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