Question

Calculate the maximum volume in ml of 0.15M HCl that each of the following antacid formulations would be expected to neutralize. Assume complete neutralization. Show your working.

a. A tablet containing 150mg Mg(OH)2

b. A tablet containing 850mg of CaCO3

Answer 1

a. 34 mL; b. 110 mL

a. A tablet containing 150 Mg(OH)₂

Mg(OH)₂ + 2HCl ⟶ MgCl₂ + 2H₂O

Moles of Mg(OH)₂ = 150 mg Mg(OH)₂ × [1 mmol Mg(OH)₂/58.32 mg Mg(OH)₂

= 2.572 mmol Mg(OH)₂

Moles of HCl = 2.572 mmol Mg(OH)₂ × [2 mmol HCl/1 mmol Mg(OH)₂]

= 5.144 mmol HCl

Volume of HCl = 5.144 mmol HCl × (1 mmol HCl/0.15 mmol HCl) = 34 mL HCl

b. A tablet containing 850 mg CaCO₃

CaCO₃ + 2HCl ⟶ CaCl₂ + CO₂ + H₂O

Moles of CaCO₃ = 850 mg CaCO₃ × [1 mmol CaCO₃/100.09 mg CaCO₃

= 8.492 mmol CaCO₃

Moles of HCl = 8.492 mmol CaCO₃ × [2 mmol HCl/1 mmol CaCO₃]

= 16.98 mmol HCl

Volume of HCl = 16.98 mmol HCl × (1 mL HCl/0.15 mmol HCl) = 110 mL HCl