1. 8.4 Percent Concentration
Chapter 8 Solutions
8.4 Percent Concentration

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

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

4. Mass of Solution

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

6. Guide to Calculating Solution Concentrations

7. Learning Check 1) 15.0%(m/m) Na2CO3 2) 6.38%(m/m) Na2CO3
A solution is prepared with 15.0 g of Na2CO3 and 235 g of H2O. What is 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

8. Solution
3) 6.00% (m/m) Na2CO3
STEP 1 Given: 15.0 g of Na2CO3; 235 g of H2O
Need: mass percent (m/m) of Na2CO3 solution
STEP 2 Plan: mass percent(m/m) = g of solute x 100%
g of solution
Calculate mass of solution
= g g
= 250 g of Na2CO3 solution

9. Solution (continued) STEP 3 Write equalities and conversion factors:
15.0 g of Na2CO3 = 250 g of solution
15.0 g Na2CO3 and g solution
250 g solution g of Na2CO3
STEP 4 Set up problem:
mass = g Na2CO3 x 100 = 6.00%(m/m) Na2CO3
percent g solution
(m/m)

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

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

12. Preparation of a Solution: Mass/Volume Percent

13. Percent Conversion Factors
Two conversion factors can be written for each type of percent concentration.

14. Learning Check Write two conversion factors for each solution:
A % (m/m) NaOH
B % (v/v) ethanol
C. 4.8% (m/v) HCl

15. Solution A. 8.50% (m/m) NaOH 8.50 g NaOH and 100 g solution
100 g solution g NaOH
B % (v/v) ethanol
5.75 mL ethanol and mL solution
100 mL solution mL ethanol
C. 4.8% (m/v) HCl
4.8 g HCl and mL HCl
100 mL solution g HCl

16. Guide to Using Concentration to Calculate Mass or Volume

17. Example of Using Percent Concentration (m/m) 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 of solution; 10.0% (m/m) NaCl
Need: g of NaCl (solute)
STEP 2 Plan: g of solution g of NaCl 17

18. Solution STEP 3 Write equalities and conversion factors:
10.0 g of NaCl = 100 g of NaCl solution
10.0 g NaCl and 100 g NaCl solution
100 g NaCl solution g NaCl
STEP 4 Set up problem to cancel grams of solution:
225 g NaCl solution x g NaCl = 22.5 g of NaCl g NaCl solution

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

20. Solution STEP 1 Given: 75.0 g of NaOH solution;
14.0% (m/m) NaOH solution
Need: g of NaOH (solute)
STEP 2 g of solution g of NaOH
STEP 3 Write equalities and conversion factors:
14.0 g of NaOH = 100 of NaOH solution
14.0 g NaOH and 100 g NaOH solution
100 g NaOH solution g NaOH
STEP 4 Set up problem to cancel the grams of solution:
75.0 g NaOH solution x g NaOH = 10.5 g of NaOH g NaOH solution

21. 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 of ethanol?
1) mL
2) mL
3) mL

22. Solution STEP 1 Given: 2.25 mL of ethanol (solute)
5.75% (v/v) ethanol solution
Need: mL of ethanol solution
STEP 2 Plan: mL of ethanol mL of solution
STEP 3 Write equalities and conversion factors:
100 mL of solution = 5.75 mL of ethanol
5.75 mL ethanol and mL solution
100 mL solution mL ethanol
STEP 4 Set up problem to cancel the mL of ethanol:
2.25 mL ethanol x 100 mL solution = mL of solution mL ethanol

23. Example Using Percent Concentration (m/v) Factors
How many mL of a 4.20% (m/v) will contain 3.15 g KCl?
STEP 1 Given: g of KCl (solute)
4.20% (m/v) KCl solution
Need: mL of KCl solution
STEP 2 Plan: g of KCl mL of KCl solution 23

24. Using Percent Concentration(m/v) Factors (continued)
STEP 3 Write equalities and conversion factors:
4.20 g KCl = 100 mL of KCl solution
4.20 g KCl and mL KCl solution
100 mL KCl solution g KCl
STEP 4 Set up the problem:
3.15 g KCl x 100 mL KCl solution = mL of KCl g KCl

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

26. Solution 2) 11.0 g of NaOH STEP 1 Given: 125 mL of NaOH (solution)
8.80% (m/v) NaOH solution
Need: g of NaOH (solute)
STEP 2 Plan: mL of NaOH solution g of NaOH

27. Solution (continued) STEP 3 Write equality and conversion factors:
8.80 g of NaOH = 100 mL of NaOH solution
8.80 g NaOH and 100 mL NaOH solution
100 mL NaOH solution g NaOH
STEP 4 Set up the problem:
125 mL NaOH solution x g NaOH
100 mL NaOH solution
= 11.0 g of NaOH