1. Percent Concentration
Chapter 7 Solutions
7.4
Percent Concentration

2. Percent Concentration
The concentration of a solution
is the amount of solute dissolved in a specific amount of solution.
amount of solute
amount of solution

3. Mass Percent Mass percent (%m/m) is the
concentration is the percent by mass of solute in a solution.
mass percent = g of solute x 100
g of solute + g of solvent
amount in g of solute in 100 g of solution.
mass percent = g of solute x 100
100 g of solution

4. Mass of Solution Add water to give 50.00 g solution 8.00 g KCl
50.00 g KCl solution
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Publishing as Benjamin Cummings

5. Calculating Mass Percent
The calculation of mass percent (%m/m) requires the
grams of solute (g KCl) and
grams of solution (g KCl solution).
g of KCl = g
g of solvent (water) = g
g of KCl solution = g
8.00 g KCl (solute) x 100 = 16.0% (m/m)
50.00 g KCl solution

6. Learning Check 1) 15.0% (m/m) Na2CO3 2) 6.38% (m/m) Na2CO3
A solution is prepared by mixing 15.0 g Na2CO3 and 235 g of H2O. Calculate the mass percent (%m/m) of the solution.
1) 15.0% (m/m) Na2CO3
2) 6.38% (m/m) Na2CO3
3) 6.00% (m/m) Na2CO3

7. Solution 3) 6.00% (m/m) Na2CO3 STEP 1 mass solute = 15.0 g Na2CO3
mass solution = g g = 250. g
STEP 2 Use g solute/ g solution ratio
STEP 3 mass %(m/m) = g solute x
g solution
STEP 4 Set up problem
mass %(m/m) = 15.0 g Na2CO3 x 100 = 6.00% Na2CO3
250. g solution

8. Volume Percent The volume percent (%v/v) is
percent volume (mL) of solute (liquid) to volume (mL) of solution.
volume % (v/v) = mL of solute x mL of solution
solute (mL) in 100 mL of solution.
volume % (v/v) = mL of solute mL of solution

9. Mass/Volume Percent The mass/volume percent (%m/v) is
percent mass (g) of solute to volume (mL) of solution.
mass/volume % (m/v) = g of solute x mL of solution
solute (g) in 100 mL of solution.
mass/volume % (m/v) = g of solute mL of solution

10. Percent Conversion Factors
Two conversion factors can be written for each type of % value.
TABLE 7.7
5% (m/v) glucose There are 5 g of glucose g glucose and mL solution
in 100 mL of solution mL solution g glucose

11. Learning Check Write two conversion factors for each solutions.
A % (m/m) NaOH
B. 5.75% (v/v) ethanol
C % (m/v) HCl

12. Solution A. 8.50 g NaOH and 100 g solution 100 g solution 8.50 g NaOH
B mL alcohol and mL solution
100 mL solution mL alcohol
C g HCl and mL HCl
100 mL solution g HCl

13. Using Percent Concentration (m/m) as Conversion Factors
How many grams of NaCl are needed to prepare
225 g of a 10.0% (m/m) NaCl solution?
STEP 1 Given: 225 g solution; 10.0% (m/m) NaCl
Need: g of NaCl
STEP 2 g solution g NaCl
STEP 3 Write the 10.0% (m/m) as conversion factors.
10.0 g NaCl and g solution
100 g solution g NaCl
STEP 4 Set up using the factor that cancels g solution.
225 g solution x g NaCl = 22.5 g NaCl g solution

14. Learning Check 75.0 g of 14.0% (m/m) NaOH solution? 1) 10.5 g NaOH
How many grams of NaOH are needed to prepare
75.0 g of 14.0% (m/m) NaOH solution?
1) 10.5 g NaOH
2) g NaOH
3) 536 g NaOH

15. Solution 1) 10.5 g NaOH 75.0 g solution x 14.0 g NaOH = 10.5 g NaOH
14.0% (m/m) factor

16. Learning Check 1) 2.56 mL 2) 12.9 mL 3) 39.1 mL
How many milliliters of a 5.75% (v/v) ethanol solution can be prepared from 2.25 mL ethanol?
1) mL
2) mL
3) mL

17. Solution 3) 39.1 mL 2.25 mL ethanol x 100 mL solution 5.75 mL ethanol
5.75% (v/v) inverted
= mL solution

18. Using Percent Concentration(m/v) as Conversion Factors
How many mL of a 4.20% (m/v) will contain 3.15 g KCl?
STEP 1 Given: g KCl(solute); 4.20% (m/v) KCl
Need: mL of KCl solution
STEP 2 Plan: g KCl mL KCl solution
STEP 3 Write conversion factors.
4.20 g KCl and mL solution
100 mL solution g KCl
STEP 4 Set up the problem
3.15 g KCl x 100 mL KCl solution = mL KCl g KCl

19. Learning Check How many grams of NaOH are needed to prepare 125
mL of a 8.80% (m/v) NaOH solution?

20. Solution How many grams of NaOH are needed to prepare 125
mL of a 8.80% (m/v) NaOH solution?
125 mL solution x g NaOH = g NaOH
100 mL solution