1. 9.4 Solution Concentrations and Reactions
Suppose we prepare a solution from 8.00 g of KI (solute) and g of water solvent).
Learning Goal Calculate the concentration of a solute in a solution; use concentration units to calculate the amount
of solute or solution. Given the volume and concentration of a solution, calculate the amount of another reactant or product in a reaction.

2. Solution Concentrations
The amount of a solute may be expressed in units of grams, milliliters, or moles.
The amount of a solution may be expressed in units of grams, milliliters, or liters.

3. Mass Percent (m/m) Concentration
Mass percent (m/m) is
the concentration by mass of solute in mass of solution.
the grams of solute in 100 grams of solution. × ×

4. Mass of Solute − Mass Solution
When g of water is added to 8.00 g of KCl, the mass percent concentration is 16.0% (m/m). × ×

5. Guide to Calculating Solution Concentration

6. Calculating Mass Percent
What is the mass percent of NaOH in a solution prepared by dissolving 30.0 g of NaOH in g of H2O?
STEP 1 State the given and needed quantities.
ANALYZE Given Needed
THE g NaOH solute mass percent
PROBLEM g NaOH g H2O = (m/m)
150.0 g of NaOH solution

7. Calculating Mass Percent
What is the mass percent of NaOH in a solution prepared by dissolving 30.0 g of NaOH in g of H2O?
STEP 2 Write the concentration expression.
STEP 3 Substitute solute and solution quantities into the expression and calculate. × ×

8. Study Check
A solution is prepared by mixing 15.0 g of Na2CO3 and 235 g of H2O. Calculate the mass percent (m/m) of the solution.
A. 15.0% (m/m) Na2CO3 solution
B % (m/m) Na2CO3 solution
C % (m/m) Na2CO3 solution

9. Solution
A solution is prepared by mixing 15.0 g of Na2CO3 and 235 g of H2O. Calculate the mass percent (m/m) of the solution.
STEP 1 State the given and needed quantities.
STEP 2 Write the concentration expression.
ANALYZE Given Need
THE g Na2CO3 solute mass percent (m/m)
PROBLEM g Na2CO g H2O = 250. g solution ×

10. Solution
A solution is prepared by mixing 15.0 g of Na2CO3 and 235 g of H2O. Calculate the mass percent (m/m) of the solution.
STEP 3 Substitute solute and solution quantities into the expression and calculate.
The answer is C, 6.00% Na2CO3 solution. ×

11. Volume Percent (v/v) Concentration
The volume percent (v/v) is the
percent volume (mL) of solute (liquid) to volume (mL) of solution.
volume of solute (mL) in 100 mL of solution (conversion factor for volume percent) ×

12. Mass/Volume Percent The mass/volume percent (m/v) is the
percent mass (g) of solute to volume (mL) of solution.
mass of solute (g) in 100 mL of solution.
(conversion factor for mass/volume percent) ×
Core Chemistry Skill Calculating Concentration

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

14. Solution
A % (m/m) NaOH
B % (v/v) ethanol
C. 4.8% (m/v) HCl

15. Molarity
Molarity (moles of solute/liter of solution) is defined as the moles of solute per volume (L) of solution.
A 1.0 M solution of NaCl is defined as

16. Molarity Calculations
What is the molarity of L of NaOH solution if it contains 6.00 g of NaOH?
STEP 1 State the given and needed quantities.
1 mole NaOH = g NaOH
ANALYZE Given Need
THE g NaOH solute molarity (mole/L)
PROBLEM L of NaOH solution ×

17. Molarity Calculations
What is the molarity of L of NaOH solution if it contains 6.00 g of NaOH?
STEP 2 Write the concentration expression.
STEP 3 Substitute solute and solution quantities into the expression and calculate.

18. Study Check
What is the molarity of L of a KNO3 solution containing 34.8 g of KNO3?
A M
B M
C M

19. Solution
What is the molarity of L of a KNO3 solution containing 34.8 g of KNO3?
STEP 1 State the given and needed quantities.
1 mole of KNO3 = g KNO3
ANALYZE Given Need
THE g KNO3 solute molarity (mole/L)
PROBLEM L of KNO3 solution ×

20. Solution
What is the molarity of L of a KNO3 solution containing 34.8 g of KNO3?
STEP 2 Write the concentration expression.
STEP 3 Substitute solute and solution quantities into the expression and calculate.
The answer is B, 1.53 M KNO3.

21. Molarity as a Conversion Factor
The units of molarity are used as conversion factors in calculations with solutions.
Molarity Equality
3.5 M HCl 1 L solution = 3.5 moles of HCl
Written as Conversion Factors

22. Conversion Factors, Concentrations
Core Chemistry Skill Using Concentration as a Conversion Factor

23. Guide to Using Concentration to Calculate Mass or Volume
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.

24. Study Check
How many grams of NaOH are needed to prepare 75.0 g of 14.0% (m/m) NaOH solution?
A g of NaOH
B g of NaOH
C. 536 g of NaOH

25. Solution
How many grams of NaOH are needed to prepare 75.0 g of 14.0% (m/m) NaOH solution?
STEP 1 State the given and needed quantities.
STEP 2 Write a plan to calculate mass or volume.
grams of grams of
solution solute
ANALYZE Given Need
THE grams of 14.0% grams NaOH
PROBLEM (m/m) NaOH solution
Percent (m/m)

26. Solution
How many grams of NaOH are needed to prepare 75.0 g of 14.0% (m/m) NaOH solution?
STEP 3 Write equalities and conversion factors.
14.0 g NaOH = 100 g of solution
STEP 4 Set up the problem to calculate mass or volume.
The answer is A, 10.5 g NaOH. ×

27. Study Check
How many grams of AlCl3 are needed to prepare 125 mL of a M solution?
A g of AlCl3
B g of AlCl3
C g of AlCl3

28. Solution
How many grams of AlCl3 are needed to prepare 125 mL of a M solution?
STEP 1 State the given and needed quantities.
STEP 2 Write a plan to calculate mass or volume.
liters of grams of
solution solute
ANALYZE Given Need
THE mL (0.125 L) solution grams AlCl3
PROBLEM M solution
Molarity

29. Solution
How many grams of AlCl3 are needed to prepare 125 mL of a M solution?
STEP 3 Write equalities and conversion factors.
moles AlCl3 = 1 L of solution
1 mole AlCl3 = g AlCl3

30. Solution
How many grams of AlCl3 are needed to prepare 125 mL of a M solution?
STEP 4 Set up the problem to calculate mass or volume.
Answer is C, 2.50 g AlCl3. × ×

31. Chemical Reactions in Solution
When chemical reactions involve aqueous solutions, we use
the balanced chemical equation,
the molarity, and
the volume
to determine the moles or grams of the reactants or products.
Core Chemistry Skill Calculating the Quantity of a Reactant or Product for a Chemical Reaction in Solution

32. Guide to Calculations Involving Solutions in Chemical Reactions
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.

33. Study Check
Zinc reacts with HCl to produce hydrogen gas, H2 , and ZnCl2.
Zn(s) + 2HCl(aq) H2(g) + ZnCl2(aq)
How many liters of a 1.50 M HCl solution completely react with 5.32 g of zinc?

34. Solution Zinc reacts with HCl to produce hydrogen gas, H2 , and ZnCl2.
Zn(s) + 2HCl(aq) H2(g) + ZnCl2(aq)
How many liters of a 1.50 M HCl solution completely react with 5.32 g of zinc?
STEP 1 State the given and needed quantities.
ANALYZE Given Need
THE g Zn
PROBLEM M HCl solution liters of HCl
Equation solution
Zn(s) + 2HCl(aq) H2(g) + ZnCl2(aq)

35. Solution Zinc reacts with HCl to produce hydrogen gas, H2 , and ZnCl2.
Zn(s) + 2HCl(aq) H2(g) + ZnCl2(aq)
How many liters of a 1.50 M HCl solution completely react with 5.32 g of zinc?
STEP 2 Write a plan to calculate the needed quantity.
moles moles volume
of of of
zinc HCl HCl
Mole–mole factor
Molarity

36. Solution Zinc reacts with HCl to produce hydrogen gas, H2, and ZnCl2.
Zn(s) + 2HCl(aq) H2(g) + ZnCl2(aq)
How many liters of a 1.50 M HCl solution completely react with 5.32 g of zinc?
STEP 3 Write equalities and conversion factors including mole–mole and concentration factors.

37. Solution Zinc reacts with HCl to produce hydrogen gas, H2, and ZnCl2.
Zn(s) + 2HCl(aq) H2(g) + ZnCl2(aq)
How many liters of a 1.50 M HCl solution completely react with 5.32 g of zinc?
STEP 4 Set up the problem to calculate needed quantity. × × ×

38. Concept Map for Chemical Equations