Answer to Question #172466 in Physical Chemistry for Gwyneth

Question

Magnesium hydroxide, the active ingredient in milk of magnesia, neutralizes stomach acid, primarily HCl, according to the reaction: 

                                Mg(OH)2 + 2 HCl à 2 H2O + MgCl2        

How much HCl in grams can be neutralized by 11.4 g of Mg(OH)2? 

Molar masses, g/mol: Mg(OH)2 = 58.33; HCl = 36.46

Answer 1

Moles of $Mg(OH)_2$ in $11.4\ g=\frac{11.4}{58.33}=$ $0.19544$

From the equation,

$Mg(OH)_2 + 2 HCl\to2 H_2O + MgCl_2$

So,for every mole of magnesium hydroxide ,two moles of $HCl$ are required.

Hence moles of $HCl$ required are $0.19544\times 2=0.39088$

Mass of $HCl$ required $=0.39088\times 36.46=14.251\ g$