Question

One brand of extra-strength antacid tablets contains 750 mg of calcium carbonate (100 g/mol) in each tablet. Stomach acid is essentially a hydrochloric acid solution. Is so much calcium carbonate really needed to neutralize stomach acid? Calculate the volume of stomach acid with a pH of 1.0 that one of these tablets could neutralize, and compare that value with the normal volume of stomach fluid, which usually is about 100 mL. One tablet can neutralize _____ mL of stomach acid at a pH of 1.0.
a. 75
b. 150
c. 250
d. 15
e. 7.5

Answer 1

Answer:

One tablet can neutralize 150 mL of stomach acid at a pH of 1.0

Explanation:

Step 1: Data given

Mass of calcium carbonate = 750 mg = 0.75 grams

Molar mass of CaCO3 = 100 g/mol

pH = 1.0

Step 2: The balanced equation

2HCl  +  CaCO3 →  CaCl2  +  H2CO3

Step 3: Calculate molarity of HCl

pH = -log[H+] = 1

[H+] = 0.1 M = 0.10 mol/L

Step 4: Calculate moles of CaCO3

Moles CaCO3 = 0.75 grams / 100g/mol

Moles CaCO3 = 0.0075 mol

Step 5: Calculate moles of HCl

For 2 moles HCl we need 1 mol CaCO3 to produce CaCl2 and 1 mole of H2CO3

For 0.0075 moles of CaCO3 we have 2*0.0075 = 0.015 moles HCl

Step 6: Calculate volume of HCl

Volume = moles /molarity

Volume = 0.015 moles / 0.1 M

Volume = 0.15 L = 150 mL

One tablet can neutralize 150 mL of stomach acid at a pH of 1.0.