Molarity & Solutions

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.

Concentration Concentration-the amount of solute that is dissolved into a solvent Concentrated-when a solution has a high concentration of solute Dilute-when a solution has a low concentration of solute

Concentration… Concentration can be described in terms of “weak” or “strong”, “concentrated” or “dilute”, but these are both relative terms and can be subjective.

Molarity Molarity is one way to measure concentration; it is the number of moles of solute per liter of solution. The unit of molarity is mol/L, which can be abbreviated with an uppercase M.

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=Moles Liter 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=Moles Liter moles of NaCl is dissolved in 4.0 L of water, calculate the molarity. Molarity=2.255 moles 4.0 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=Moles Liter moles of NaCl is dissolved in 4.0 L of water, calculate the molarity. Molarity = moles =0.56 moles = 0.56 M(Molar) 4.0 L Liter

g KOH is dissolved in 250. mL of water, calculate the molarity. Molarity=

g KOH is dissolved in 250. mL of water, calculate the molarity. Molarity=5.00 g 1

g KOH is dissolved in 250. mL of water, calculate the molarity. K = 39.0 (mass off periodic table) O = 16.0 H = g/mol Molarity=5.00 g x 1 mole g

g KOH is dissolved in 250. mL of water, calculate the molarity. K = 39.0 (mass off periodic table) O = 16.0 H = g/mol Molarity=5.00 g x 1 mole g L

g KOH is dissolved in 250. mL of water, calculate the molarity. K = 39.0 (mass off periodic table) O = 16.0 H = g/mol Molarity=5.00 g x 1 mole g L =0.356 M

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

0.172 moles 1 L

3.How many moles are there in 205. mL of a M solution? moles x L 1 L1

3.How many moles are there in 205. mL of a M solution? moles x L = moles 1 L1

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

4.How many grams NaCl are there in mL of M solution? L 1

4.How many grams NaCl are there in mL of M solution? L x0.500 moles 11 L

4.How many grams NaCl are there in mL of M solution? L x0.500 molesx 58.5 g 11 L 1 mole

4.How many grams NaCl are there in mL of M solution? L x0.500 molesx 58.5 g=7.31 g 1 1 L 1 mole

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

L 1

5.How many grams of NaCl must be used to prepare a mL of M solution L x moles 1 1 L

5.How many grams of NaCl must be used to prepare a mL of M solution L x moles x 58.5 g 1 1 L 1 mole

5.How many grams of NaCl must be used to prepare a mL of M solution L x moles x 58.5 g = 1.46 g 1 1 L 1 mole

6.How many milliliters of a M solution of CoCl 2 will contain 25.0 g?

25.0 g 1

6.How many milliliters of a M solution of CoCl 2 will contain 25.0 g? 25.0 g x 1 mole g

6.How many milliliters of a M solution of CoCl 2 will contain 25.0 g? 25.0 g x 1 mole x 1 L g mol

6.How many milliliters of a M solution of CoCl 2 will contain 25.0 g? 25.0 g x 1 mole x 1 L x1000 mL g mol 1 L

6.How many milliliters of a M solution of CoCl 2 will contain 25.0 g? 25.0 g x 1 mole x 1 L x1000 mL = 962 mL g mol 1 L

7.Describe how you would prepare mL of a M solution of CoCl L x moles x g = 2.60 g 1 L 1 mole Weigh 2.60 g of CoCl 2 Dissolve in water Transfer to a 100 mL volumetric flask and fill to the line