Question

If you want to increase the pH of the stomach from 1.00 to 2.00 using an antacid tablet, how many grams of CaCO3 will be required to change the pH value? Assume the acid is HCl and you have 1.00L stomach volume.

Answer 1

CaCO3 + 2HCl ==> CaCl2 + CO2 + H2O

1 mole CaCO3 = 2 moles HCl

if pH = 1, [H3O+] =0.1 M

concentration of HCL in stomach = 0.1 moles/liter

if pH = 2 , [H3O+] =0.01 M

concentration of HCL in stomach = 0.01 M = 0.01 moles/liter

decrease in concentration of HCL = 0.1 - 0.01 = 0.09 moles

so that , 0.09 mole of HCl required 0.09/2= 0.045 mole of CaCo3

grams CaCO3 needed = n*M

                = 0.045 moles x 100 g/mole

                 = 4.5 grams