Question

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.) Express the volume in millilite rs to two significant figures.

Answer 1

Answer:

1.5 ml

Explanation:

Assuming that the stomach acid is HCl then:

Mg(OH)₂ + 2HCl → MgCl₂ + H₂O

since

number of moles of Mg(OH)₂ = mass / molecular weight of Mg(OH)₂ = 3*400 mg / 58.3 gr/mol = 20.583 m mol

thus

number of moles of HCl required = number of moles of Mg(OH)₂*2 = 41.166 m mol  = 41.166 m moles

knowing that

density = mass / volume = (molecular weight* moles) / volume

volume =(molecular weight* moles)/ density

thus for HCl

volume =  (36.46 gr/mol * 41.166*10^-3 moles)/( 1 gr/cm³)= 1.5 cm³= 1.5 ml