concentrations of solutions prentice-hall chapter 16.2 dr. yager

Concentrations of Concentrations of SolutionsSolutions

Prentice-Hall Chapter 16.2Prentice-Hall Chapter 16.2

Dr. YagerDr. Yager

ObjectivesObjectives

SolveSolve problems involving the molarity of a problems involving the molarity of a solutionsolution

DescribeDescribe the effect of dilution on the total the effect of dilution on the total moles of solute in solutionmoles of solute in solution

DefineDefine percent by volume and percent by percent by volume and percent by massmass

MolarityMolarity

solvent of liters

solute of moles (M) Molarity

solution of liters

solute of moles (M) Molarity

To make a 0.5 molar (0.5M) solution, first add 0.5 mol of solute to a 1-L volumetric flask half filled with distilled water.

Swirl the flask carefully to dissolve the solute.

Fill the flask with water exactly to the 1-Liter mark.

A solution has a volume of 2.0 L and contains 36.0 g of glucose (C6H12O6). If the molar mass of glucose is 180 g/mol, what is the molarity of the solution?

glucose M .10 solution of liter 2.0

glucose mol .20 Molarity

solution of liter 1

solute of moles Molarity

0.20mol

molglucose

g 180

glucose g 36 glucose of moles

Household laundry bleach is a dilute aqueous solution of sodium hypochlorite (NaClO). How many moles of solute are present in 1.5 L of 0.07 M NaClO?

NaClO mol 0.11 solution L 1.5 x solution L 1.0

NaClO mol 0.07solution of L 1.0

NaClO of mol 0.07 M 0.07

How many moles of solute are in 250 ml of 2.0M CaCl2? How many grams of CaCl2 is this?

22

22

2

CaCl g 56. mol

g 111. x CaCl mol .50

CaCl mol .50 solution L .25 x solution L 1.0

CaCl mol 2.0solution of L 1.0

CaCl of mol 2.0 M 2.0

The The concentrationconcentration of a solution is a measure of of a solution is a measure of the amount of solute that is dissolved in a given the amount of solute that is dissolved in a given quantity of solvent.quantity of solvent.

A A dilute solutiondilute solution is one that contains a small is one that contains a small amount of solute. amount of solute.

AA concentratedconcentrated solutionsolution contains a large contains a large amount of solute.amount of solute.

Key IdeaKey Idea

Diluting a solution reduces the number of moles Diluting a solution reduces the number of moles of solute per unit volume, but the total number of of solute per unit volume, but the total number of moles of solute in solution does not change.moles of solute in solution does not change.

Making DilutionsMaking Dilutions

The total number of moles of solute remains The total number of moles of solute remains unchanged upon dilution, so you can write this unchanged upon dilution, so you can write this equation.equation.

MM11 and and VV11 are the molarity and volume of the are the molarity and volume of the initial solution, and initial solution, and MM22 and and VV22 are the molarity are the molarity and volume of the diluted solution.and volume of the diluted solution.

Making a Dilute SolutionMaking a Dilute Solution

To prepare 100 ml of 0.40M MgSO4 from a stock solution of 2.0M MgSO4, a student first measures 20 mL of the stock solution with a 20-mL pipet.

She then transfers the 20 mL to a 100-mL volumetric flask.

Finally she carefully adds water to the mark to make 100 mL of solution.

Volume-Measuring Devices

How many milliliters of a solution of 4.00 M KI are needed to prepare 250.0 ml of 0.760 M KI?

M1 x V1 = M2 x V2

4.00 M x V1 = 0.760 M x 250.0 ml

V1 = 47.5 ml

Percent SolutionsPercent Solutions

The concentration of a solution in percent can The concentration of a solution in percent can be expressed in two ways: as the ratio of the be expressed in two ways: as the ratio of the volume of the solute to the volume of the volume of the solute to the volume of the solution or as the ratio of the mass of the solution or as the ratio of the mass of the solute to the mass of the solution.solute to the mass of the solution.

Concentration in Percent Concentration in Percent (Volume/Volume)(Volume/Volume)

Isopropyl alcohol (2-propanol) is sold as a 91% solution. This solution consist of 91 mL of isopropyl alcohol mixed with enough water to make 100 mL of solution.

A bottle of the antiseptic hydrogen peroxide (H2O2) is labeled 3.0% (v/v). How many milliliters of H2O2 are in a 400.0 ml bottle of this solution?

100% x solution of volume

solute of volume (%(v/v)) volume byPercent

2222

22

OH of ml 12 OH of volume Unknown

100% x ml 400.0

OH of volume Unknown 3.0

%

Concentration in Percent Concentration in Percent (Mass/Mass)(Mass/Mass)

A bottle of glucose is labeled 2.8% (m/m). How many grams of glucose are in 2000.0 g of solution?

100% x solution of mass

solute of mass (%(m/m)) volume byPercent

glucose of g 56 glucose of mass Unknown

100% x 2000.0g

glucose of mass Unknown 82

%.

1. To make a 1.001. To make a 1.00MM aqueous solution of aqueous solution of NaCl, 58.4 g of NaCl are dissolved inNaCl, 58.4 g of NaCl are dissolved in

a.a. 1.00 liter of water.1.00 liter of water.

b.b. enough water to make 1.00 liter solution.enough water to make 1.00 liter solution.

c.c. 1.00 kg of water.1.00 kg of water.

d.d. 100 mL of water.100 mL of water.

2. What mass of sodium iodide (NaI) is 2. What mass of sodium iodide (NaI) is contained in 250 mL of a 0.500contained in 250 mL of a 0.500MM solution? solution?

a.a. 150 g150 g

b.b. 75.0 g75.0 g

c.c. 18.7 g18.7 g

d.d. 0.50 g 0.50 g

3. Diluting a solution does NOT change 3. Diluting a solution does NOT change which of the following? which of the following?

a.a. concentrationconcentration

b.b. volumevolume

c.c. milliliters of solventmilliliters of solvent

d.d. moles of solutemoles of solute

4. In a 2000 g solution of glucose that is 4. In a 2000 g solution of glucose that is labeled 5.0% (m/m), the mass of labeled 5.0% (m/m), the mass of waterwater is is

a.a. 2000 g. 2000 g.

b.b. 100 g. 100 g.

c.c. 1995 g. 1995 g.

d.d. 1900 g.1900 g.