Solutions and Concentrations

Notes Page 5

SOLUTIONS

A homogenous mixture of two or more substances

2 PARTS OF A SOLUTION• SOLUTE• A solute is the dissolved substance in a solution.

Sugar in sodaCarbon dioxide in sodaSalt in salt water

• SOLVENT• A solvent is the dissolving medium in a solution. • Water in salt water

Water in soda

Molarity = concentration•Amount of substance (mol)•Volume of mixture (L)

•Unit = mol/L or M•1.0 M = 1 molar •12.0 M = 12 molar

solUTE over solVENT

Example 1•1.5 mol of NaCl are dissolved in 1 L of water. What is the molarity of the solution?

•1.5 mol NaCl = 1.5 mol/L or 1.5 M•1 L H2O

Example 2•100 g of NaCl are dissolved in 1 L of water.

What is the molarity of the solution?

•100 g NaCl |1 mol NaCl = 1.71 mol 58.44 g NaCl

•1.71 mol NaCl = 1.71 M 1 L

Example 3

•100 g of NaCl are dissolved in 250 mL of water. What is the molarity of the solution? •100 g NaCl |1 mol NaCl = 1.71mol• 58.44 g NaCl •250 mL / 103 mL = 0.25 L•1.71 mol NaCl = 6.84 M 0.25 L

Example 4• How many moles of NaCl are in 500 mL of a 0.25 M solution? • Basic formula: M = mol L • Convert: 500 mL = 0.5 L

• 0.25 M = mol = 0.5 L x 0.25 M = mol 0.5 L

= 0.125 mol NaCl

Example 5• How many grams of NaCl are in 500 mL of a 2.25 M solution? • Basic formula: M = mol L • Convert: 500 mL = 0.5 L

• 2.25 M = mol = 0.5 L x 2.25 M = mol 0.5 L = 1.125 mol NaCl • 1.125 mol NaCl | 58.44 g NaCl = 65.75 g NaCl 1 mol