Topic 6. 5 Solutions

Solutions are homogeneous mixtures. The most common way to express solution concentration is by molarity.

Molarity The molarity of a solution indicates the moles of solute per liter of solution M = moles solute/L of solution

Concentrated vs. Dilute Concentrated= large amount of solute in a small amount of solvent Dilute= small amount of solute in a large amount of solvent

Saturated Saturated solutions have the maximum molarity at a given temperature. (The maximum amount of solute that will dissolve at that temperature)

8 moles / 8 Liters = 1 M

4 moles / 4 Liters = 1 M

2 moles / 2 Liters = 1 M

Calculating Molarity 1.Grams  moles 2.mL  L 3.M = moles of solute liters of solution

Steps involved in preparing solutions from pure solids

Ex. 1)  find the molarity of a solution when you dissolve 5.00g of CaCl 2 in enough water to make 500ml of solution;

1) find moles of CaCl 2 in 5.00g: 5.00 gCaCl 2 x (1mole CaCl 2 ) = (111 g CaCl 2 ) = moles CaCl 2

2) find volume in liters: 500 ml x (1 L) = (1000 ml) = L

2) calculate molarity: moles CaCl 2 = L = M

To find the new concentration, M, of each solution above when diluted to 800ml; M 1 x V 1 = M 2 x V 2 (moles before = moles after)