Question

The label on liquid Gaviscon states that each tablespoon (15mL) contains 95mg of aluminum hydroxide, Al(OH)3, and 412 mg of magnesium carbonate, MgCO3. How many moles of hydronium ion can be neutralized by one tablespoon of Gaviscon?

Answer 1

Number of moles of Al(OH)3 = 95 * 10^-3/78 = 1.21 *10^-3 moles
The neutralisation reaction can be written as
Al(OH)3 + 3H+ -----> Al(+3) + 3H2O.
So each mole of Al(OH)3 can neutralize 3 moles of hydronium ions. So, the number of hydronium ions that are neutralised by Al(OH)3 alone = 3.65 *10^-3

Number of moles of MgCO3 = 412 * 10^-3/84.32 = 4.88 * 10^-3 moles

The neutralisation reaction can be written as
MgCO3 + 2H(+) ----> Mg(+2) + H2CO3
So, each mole of magnesium hydroxide can neutralize 2 moles of hydronium ions.
So, the number of hydronium ions neutralized by magnesium carbonate alone = 9.77 *10^-3 moles

Total number of moles of H3O + = 9.77 *10^-3 + 4.88* 10^-3 = 1.465 * 10^-2 moles <<<<<------(ANSWER)