Question

The daily output of stomach acid (gastric juice) is 1000 to 2000 mL. Prior to a meal, stomach acid (HCl) typically has a pH of 1.50

-what is the [H3O] of stomach acid?

-Given that the antacid milk of magnesia contains 400. mg of Mg(OH)2 per teaspoon, calculate the number of milliliters of stomach acid that are neutralized by 1 tablespoon of milk of magnesia. (1 tablespoon = 3 teaspoons.)

Answer 1

# [H₃O⁺] = 10^-pH

= 10^-1.5 = 0.03162

[H₃O⁺] = 0.03162 M

# 1 tablesoon = 3 teaspoon

1 teaspoon contain 400 mg of Mg(OH)₂ then 1 tablespoon contain 400 X 3 = 1200 mg of Mg(OH)₂

1200 mg = 1.2 gm

tablespoon contain 1.2 gm Mg(OH)₂

Balanced ceemical reaction berween HCl and Mg(OH)₂ is

2HCl + Mg(OH)₂   MgCl₂ + 2H₂O

molar mass of Mg(OH)₂ = 58.3197 gm/mole then 1.2 gm Mg(OH)₂ = 1.2 / 58.3197 = 0.020576 mole

According to raction for 1 mole of Mg(OH)₂ require 2 mole of HCl then for to react with 0.020576 mole of Mg(OH)₂

required HCl = 0.020576 X 2 = 0.04115 mole of HCl

HCl is strong acid dissociate completly therefore [HCl] = [H₃O⁺] = 0.03162 M

Volume of solution in liter = no. of mole / molarity

volume of HCl neutrilized = 0.04115 / 0.03162 = 1.3 liter

1.3 liter = 1300 ml

1300 ml of stomach acid that are neutralized by 1 tablespoon of milk of magnesia.