State an equation for the reactions that occur in the stomach for both substances with hydrochloric acid.

Aluminium hydroxide:

Calcium carbonate:

A typical antacid tablet has a mass of about 1 g. Determine which of the two antacids will neutralize the greater amount of hydrochloric acid if tablets of each are added to separate samples of acid. A detailed calculation is not required.

Potassium hydroxide also neutralizes hydrochloric acid. Suggest why it is not used as an antacid.

\({\text{Al(OH}}{{\text{)}}_3}{\text{(s)}} + {\text{3HCl(aq)}} \to {\text{AlC}}{{\text{l}}_3}{\text{(aq)}} + {\text{3}}{{\text{H}}_2}{\text{O(l)}}\);

\({\text{CaC}}{{\text{O}}_3}{\text{(s)}} + {\text{2HCl(aq)}} \to {\text{CaC}}{{\text{l}}_2}{\text{(aq)}} + {{\text{H}}_2}{\text{O(l)}} + {\text{C}}{{\text{O}}_2}{\text{(g)}}\);

Ignore state symbols.

\({\text{Al(OH}}{{\text{)}}_{\text{3}}}\) has smaller molar mass (so more moles per tablet);

one mole of \({\text{Al(OH}}{{\text{)}}_{\text{3}}}\) neutralizes more moles of acid;

OR

(for Al(OH)₃) \({n_{^{{\text{HCL}}}}} = \frac{3}{{78}}{\text{ (mol)}}\);

(for CACO₃) \({n_{^{{\text{HCL}}}}} = \frac{2}{{100}}{\text{ (mol)}}\);

strong (soluble) base/alkali;

damage to/corrosive to body/tissue;

There were various interpretations of the formula of aluminium hydroxide in (a) and many were able to gain one mark, the stoichiometric mark, in (b). Many did not realize that molar mass is also of consequence. Part (c) was a source of concern with many candidates showing an absolute lack of knowledge of potassium hydroxide and its chemical nature. Indeed, many seemed to think that we were asking about potassium itself! One common answer was that KOH only neutralizes one mole of HCl. The answers to (d) were either very good or somewhat vague and lacked specific reference to how placebos are used in drug development.

There were various interpretations of the formula of aluminium hydroxide in (a) and many were able to gain one mark, the stoichiometric mark, in (b). Many did not realize that molar mass is also of consequence. Part (c) was a source of concern with many candidates showing an absolute lack of knowledge of potassium hydroxide and its chemical nature. Indeed, many seemed to think that we were asking about potassium itself! One common answer was that KOH only neutralizes one mole of HCl. The answers to (d) were either very good or somewhat vague and lacked specific reference to how placebos are used in drug development.

There were various interpretations of the formula of aluminium hydroxide in (a) and many were able to gain one mark, the stoichiometric mark, in (b). Many did not realize that molar mass is also of consequence. Part (c) was a source of concern with many candidates showing an absolute lack of knowledge of potassium hydroxide and its chemical nature. Indeed, many seemed to think that we were asking about potassium itself! One common answer was that KOH only neutralizes one mole of HCl. The answers to (d) were either very good or somewhat vague and lacked specific reference to how placebos are used in drug development.