The Foundations of Chemistry

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Multiplication of the mass of the solution, 200. grams, by this unit factor gives the mass of

NiSO 4 in the solution.

Solution

__? g NiSO 4 200. g soln12.0 g NiSO 4

EXAMPLE 3-14 Mass of Solution

A 6.00% NiSO 4 solution contains 40.0 g of NiSO 4. Calculate the mass of the solution.

Plan

Placing 100. g of solution over 6.00 g of NiSO 4 gives the desired unit factor.

Solution

__? g soln40.0 g NiSO 4 667 g soln

EXAMPLE 3-15 Mass of Solute

Calculate the mass of NiSO 4 present in 200. mL of a 6.00% solution of NiSO 4. The density

of the solution is 1.06 g/mL at 25°C.

Plan

The volume of a solution multiplied by its density gives the mass of solution (see Section

1-11). The mass of solution is then multiplied by the mass fraction due to NiSO 4 (6.00 g

NiSO 4 /100. g soln) to give the mass of NiSO 4 in 200. mL of solution.

Solution

__? g NiSO 4 200. mL soln12.7 g NiSO 4

212 g soln

You should now work Exercise 55.

EXAMPLE 3-16 Percent Solute and Density

What volume of a solution that is 15.0% iron(III) nitrate contains 30.0 g of Fe(NO 3 ) 3? The

density of the solution is 1.16 g/mL at 25°C.

Plan

Two unit factors relate mass of Fe(NO 3 ) 3 and mass of solution, 15.0 g Fe(NO 3 ) 3 /100 g and

100 g/15.0 g Fe(NO 3 ) 3. The second factor converts grams of Fe(NO 3 ) 3 to grams of solution.

Solution

__? mL soln30.0 g Fe(NO 3 ) 3 172 mL

200 g soln

1.00 mL soln



1.16 g soln

100. g soln
     
     15.0 g Fe(NO 3 ) 3

6.00 g NiSO 4



100. g soln

1.06 g soln



1.00 mL soln

100. g soln
     
     6.00 g NiSO 4

6.00 g NiSO 4



100. g soln

104 CHAPTER 3: Chemical Equations and Reaction Stoichiometry

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