 Concentrations of Solutions

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Concentrations of Solutions
Prentice-Hall Chapter 16.2 Dr. Yager

Objectives Solve problems involving the molarity of a solution
Describe the effect of dilution on the total moles of solute in solution Define percent by volume and percent by mass

Molarity

To make a 0. 5 molar (0. 5M) solution, first add 0
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
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?

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?

How many moles of solute are in 250 ml of 2. 0M CaCl2
How many moles of solute are in 250 ml of 2.0M CaCl2? How many grams of CaCl2 is this?

The concentration of a solution is a measure of the amount of solute that is dissolved in a given quantity of solvent. A dilute solution is one that contains a small amount of solute. A concentrated solution contains a large amount of solute.

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

The total number of moles of solute remains unchanged upon dilution, so you can write this equation.
M1 and V1 are the molarity and volume of the initial solution, and M2 and V2 are the molarity and volume of the diluted solution.

Making a Dilute Solution

To prepare 100 ml of 0. 40M MgSO4 from a stock solution of 2
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
How many milliliters of a solution of 4.00 M KI are needed to prepare ml of M KI? M1 x V1 = M2 x V2 4.00 M x V1 = M x ml V1 = 47.5 ml

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

Concentration in Percent (Volume/Volume)

Isopropyl alcohol (2-propanol) is sold as a 91% solution
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
A bottle of the antiseptic hydrogen peroxide (H2O2) is labeled 3.0% (v/v). How many milliliters of H2O2 are in a ml bottle of this solution?

Concentration in Percent (Mass/Mass)

A bottle of glucose is labeled 2. 8% (m/m)
A bottle of glucose is labeled 2.8% (m/m). How many grams of glucose are in g of solution?

1. To make a 1. 00M aqueous solution of NaCl, 58
1. To make a 1.00M aqueous solution of NaCl, 58.4 g of NaCl are dissolved in 1.00 liter of water. enough water to make 1.00 liter solution. 1.00 kg of water. 100 mL of water.

1. To make a 1. 00M aqueous solution of NaCl, 58
1. To make a 1.00M aqueous solution of NaCl, 58.4 g of NaCl are dissolved in 1.00 liter of water. enough water to make 1.00 liter solution. 1.00 kg of water. 100 mL of water.

2. What mass of sodium iodide (NaI) is contained in 250 mL of a 0
2. What mass of sodium iodide (NaI) is contained in 250 mL of a 0.500M solution? 150 g 75.0 g 18.7 g 0.50 g

2. What mass of sodium iodide (NaI) is contained in 250 mL of a 0
2. What mass of sodium iodide (NaI) is contained in 250 mL of a 0.500M solution? 150 g 75.0 g 18.7 g 0.50 g

3. Diluting a solution does NOT change which of the following?
concentration volume milliliters of solvent moles of solute

3. Diluting a solution does NOT change which of the following?
concentration volume milliliters of solvent moles of solute

4. In a 2000 g solution of glucose that is labeled 5
4. In a 2000 g solution of glucose that is labeled 5.0% (m/m), the mass of water is 2000 g. 100 g. 1995 g. 1900 g.

4. In a 2000 g solution of glucose that is labeled 5
4. In a 2000 g solution of glucose that is labeled 5.0% (m/m), the mass of water is 2000 g. 100 g. 1995 g. 1900 g.