1. Hydrochloric acid and sodium hydroxide react as follows: (balance the equatio

Question

1. Hydrochloric acid and sodium hydroxide react as follows: (balance the equation)

HCl + NaOH --> H2O + NaCl

a. If 2.5 moles of hydrochloric acid and 3.2 moles of sodium hydroxide react to completion (i.e. until one of them is used up), show which reagent is the limiting reagent.

b. What is the greatest amount of NaCl that can be formed under these conditions?

2. Magnesium hydroxide and nitric acid react as follows: (balance the equation)

Mg(OH)2 + HNO3 --> H2O + Mg(NO3)2

a. If 2.5 moles of nitric acid and 3.8 moles of magnesium hydroxide react to completion (i.e. until one of them is used up), show which reagent is the limiting reagent.

b. What is the greatest amount of Mg(NO3)2 that can be formed under these conditions?

Explanation / Answer

(1) (a) HCl + NaOH => H2O + NaCl

Theoretical moles of HCl : NaOH = 1 : 1

Actual moles of HCl : NaOH = 2.5 : 3.2 = 1 : 1.28


Since NaOH is in excess => HCl is the limiting reagent


(b) Moles of NaCl = moles of HCl = 2.5 mol

(Mass of NaCl = moles x molar mass of NaCl = 2.5 x 58.4 = 146 g)


(2) (a) Mg(OH)2 + 2 HNO3 => 2 H2O + Mg(NO3)2

Theoretical moles of Mg(OH)2 : HNO3 = 1 : 2

Actual moles of Mg(OH)2 : HNO3 = 3.8 : 2.5 = 1.52 : 1 = 3.04 : 2


Since Mg(OH)2 is in excess => HNO3 is the limiting reagent


(b) Moles of Mg(NO3)2 = 1/2 x moles of HNO3

= 1/2 x 2.5 = 1.25 mol

(Mass of Mg(NO3)2 = moles x molar mass of Mg(NO3)2 = 1.25 x 148.3 = 185 g)

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