Magnesium hydroxide, the active ingredient in milk of magnesia, neutralizes stomach acid, primarily HCl, according to the reaction Mg (OH) 2 (aq) + 2HCl (aq) →2H2O (l) + MgCl2 (aq) What mass of HCl, in grams, is neutralized by a dose of milk of magnesia containing 3.26 g of Mg (OH) 2? Express the mass in grams to three significant figures.

Question

Chemistry

Steven Stephenson

11 March, 04:33

Magnesium hydroxide, the active ingredient in milk of magnesia, neutralizes stomach acid, primarily HCl, according to the reaction Mg (OH) 2 (aq) + 2HCl (aq) →2H2O (l) + MgCl2 (aq) What mass of HCl, in grams, is neutralized by a dose of milk of magnesia containing 3.26 g of Mg (OH) 2? Express the mass in grams to three significant figures.

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Kristin Rowland · Answer 1

For reaction stoichiometry problems like this, convert given data to moles and set up a ratio expression that relates to the balanced equation. That is ...

Given Rxn = > Mg (OH) ₂ + 2HCl = > 2H₂O + MgCl₂

Given mass = > 3.26g = (3.26g) / (58g/mol) = 0.056 mole Mg (OH) ₂

If from equation 1 mole Mg (OH) ₂ reacts with 2 moles HCl

then, 0.056 mole Mg (OH) ₂ reacts with x moles HCl

Setting up ratio and proportion expression ...

=> (1 mole Mg (OH) ₂) / (0.056 mole Mg (OH) ₂) = (2 moles HCl) / x

=> x = [2 (0.056) / (1) ] mole HCl neutralized = 0.112mole HCl (36g/mol)

= 4.05 grams of HCl neutralized.