Chemistry 11

Introduction to Molarity

Lesson 1

Prescription drugs in the correct concentration make you better.In higher concentration they can kill you.

Chemists need to make solutions that have precise concentrations

Pesticides must be in proper concentrations.

Food additives must be in correct concentrations.

A driver is legally impaired at 0.08 mg/mL blood alcohol content.

Chemists control the concentration of chemicals using the concepts we will develop in this unit.

The concentration of a solution tells you how much solute that is dissolved in a given amount of solvent (water).

The molarity is the concentration of a solution.

Molarity = MolesLitre

1. 2.255 moles of NaCl is dissolved in 4.0 L of water, calculate the molarity.

Molarity =

The concentration of a solution tells you how much solute that is dissolved in a given amount of solute (water).

The molarity is the concentration of a solution.

Molarity = MolesLitre

1. 2.255 moles of NaCl is dissolved in 4.0 L of water, calculate the molarity.

Molarity = 2.255 moles4.0 L

The concentration of a solution tells you how much solute that is dissolved in a given amount of solute (water).

The molarity is the concentration of a solution.

Molarity = MolesLitre

1. 2.255 moles of NaCl is dissolved in 4.0 L of water, calculate the molarity.Molarity = 2.255 moles

4.0 L

= 0.56 moles/litre

= 0.56 M (Molar)where M means moles per 1 litre

2. 5.00 g KOH is dissolved in 250. mL of water, calculate the molarity.

Molarity =

2. 5.00 g KOH is dissolved in 250. mL of water, calculate the molarity.

Molarity = 5.00 g

2. 5.00 g KOH is dissolved in 250. mL of water, calculate the molarity.

Molarity = 5.00 g x 1 mole56.11 g

2. 5.00 g KOH is dissolved in 250. mL of water, calculate the molarity.

Molarity = 5.00 g x 1 mole56.11 g

0.250 L

2. 5.00 g KOH is dissolved in 250. mL of water, calculate the molarity.

Molarity = 5.00 g x 1 mole56.11 g

---------------------------0.250 L

= 0.356 M

3. How many moles are there in 205. mL of a 0.172 M solution?

3. How many moles are there in 205. mL of a 0.172 M solution?

0.205 L

3. How many moles are there in 205. mL of a 0.172 M solution?

0.205 L x 0.172 moles1 L

3. How many moles are there in 205. mL of a 0.172 M solution?

0.205 L x 0.172 moles = 0.0353 moles1 L

4. How many grams NaCl are there in 250.0 mL of 0.500 M solution?

4. How many grams NaCl are there in 250.0 mL of 0.500 M solution?

0.250 L

4. How many grams NaCl are there in 250.0 mL of 0.500 M solution?

0.250 L x 0.500 moles

1 L

4. How many grams NaCl are there in 250.0 mL of 0.500 M solution?

0.250 L x 0.500 moles x 58.5 g

1 L 1 mole

4. How many grams NaCl are there in 250.0 mL of 0.500 M solution?

0.250 L x 0.500 moles x 58.5 g = 7.31 g

1 L 1 mole

5. How many grams of NaCl must be used to prepare a 100.0 mL of 0.250 M solution.

5. How many grams of NaCl must be used to prepare a 100.0 mL of 0.250 M solution.

0.1000 L

5. How many grams of NaCl must be used to prepare a 100.0 mL of 0.250 M solution.

0.1000 L x 0.250 moles 1 L

5. How many grams of NaCl must be used to prepare a 100.0 mL of 0.250 M solution.

0.1000 L x 0.250 moles x 58.5 g 1 L 1 mole

5. How many grams of NaCl must be used to prepare a 100.0 mL of 0.250 M solution.

0.1000 L x 0.250 moles x 58.5 g = 1.46 g1 L 1 mole

6. How many millilitres of a 0.200 M solution of CoCl2 will contain 25.0 g?

6. How many millilitres of a 0.200 M solution of CoCl2 will contain 25.0 g?

25.0 g

6. How many millilitres of a 0.200 M solution of CoCl2 will contain 25.0 g?

25.0 g x 1 mole 129.9 g

6. How many millilitres of a 0.200 M solution of CoCl2 will contain 25.0 g?

25.0 g x 1 mole x 1 L 129.9 g 0.200 mol

6. How many millilitres of a 0.200 M solution of CoCl2 will contain 25.0 g?

25.0 g x 1 mole x 1 L x 1000 mL 129.9 g 0.200 mol 1 L

6. How many millilitres of a 0.200 M solution of CoCl2 will contain 25.0 g?

25.0 g x 1 mole x 1 L x 1000 mL = 962 mL 129.9 g 0.200 mol 1 L

7. Describe how you would prepare 100.0 mL of a 0.200 M solution of CoCl2.

0.1000 L x 0.200 moles x 129.9 g = 2.60 g1 L 1 mole

Weigh 2.60 g of CoCl2

Dissolve in water

Transfer to a 100 mL volumetric flask and fill to the line