Question

Stomach acid is maintained by a protein pump to a pH of 1.5-3.5. If we assume that Hydrochloric acid is the only acid and its highest level of 160mM (millimolar) at the empty volume of 75mL (adults), how many kilograms of the antacid Aluminum Hydroxide would be required to bring the pH to 7?

Answer 1

Solution:

For the pH = 7, all HCl must be neutralized by Al(OH)3.

Thus, for complete neutralization,

Number of moles of HCl = Number of moles of Al(OH)3

Number of moles of HCl is calculated as,

Number of moles of HCl = Molarity x volume in L

= 0.160 M x 0.075 L = 0.012 moles

Thus, number of moles of Al(OH)3 is also equal to 0.012 moles.

Mass of Al(OH)3 = number of moles x molar mass of Al(OH)3

= 0.012 mol x 78.0 g mol-1 = 0.936 g

Mass of Al(OH)3 = 0.936 g = 0.000936 kg

= 9.36 x 10^-4 kg