Transcript Chapter 8 Solution

Chapter 8 Solution
Percent Concentration
Percent Concentration
Describes the amount of solute
dissolved in 100 parts of solution
mass % = g solute
g solution
=
g solute
g solute + g solvent
Sample Problem
Determine the % mass of a solution
containing 4.0 g KCl and 46.0 g of H2O
Solute
+
Solvent
4.0 g KCl
46.0 g H2O
50.0 g KCl solution
Calculating Mass-Mass %
g of KCl
g of solvent
g of solution
=
=
=
4.0 g
46.0 g
50.0 g
% mass = 4.0 g KCl (solute) x 100 = 8.0% KCl
50.0 g KCl sol’n
Sample Problem
A solution contains 15 g Na2CO3 and 235 g
of H2O? What is the mass % of the
solution?
1) 15% Na2CO3
2) 6.4% Na2CO3
3) 6.0% Na2CO3
Solution
mass solute
=
15 g Na2CO3
mass solution
=
15 g + 235 g = 250 g
%
= 15 g Na2CO3
x
250 g solution
= 6.0% Na2CO3 solution
100
Sample Problem
An IV solution is prepared by
dissolving 25 g glucose
(C6H12O6) into 475 g water.
What is the percent mass of
the glucose in the IV solution?
1) 5.0%
2) 20.%
3) 50.%
Solution
1) 5.0%
% mass
=
25 g glucose x 100
500. g solution
= 5.0 % glucose solution
Sample Problem

A solution is 25.0 % KOH by mass.
Calculate the grams of KOH in 170.0 g
of solution.
25.0% =
x g KOH
170.0 g sol'n
25.0 x 170.0 = x g KOH
100
x = 42.5 g KOH
x 100
Sample Problem

A solution of NaCl is needed. How many
grams of water must be added to 20.0 g of
NaCl to produced a 5.00% NaCl solution?
5.00% =
20.00 g NaCl
x 100
(20.00 g NaCl + x g H2O)
5.00(20.00 + x) = 20.00 x 100
100. + 5x = 2000
x = 380 g H2O