8.2 Measuring Concentration Objective 2 Chemistry

Essential Questions What are ppm and ppb and what are they used for? How do you calculate molarity? How do you calculate molality?

Measurement of Concentration (don’t need to write down) There are many ways to indicate concentration Molarity Molality Mole fraction Weight/volume percent Volume/volume percent Parts per million and parts per billion Different fields of sciences use different ways

“Parts Per” Used to measure very, very small concentrations Usually used for trace elements in the earth or toxins present in the environment Parts Per million (ppm) – one out of every one million parts Others are ppb, and ppt

Molarity (M) Most useful in chemistry for liquid solutions Note: 1 L = 1000 mL

Molarity (cont) Find molarity for the following: 4.4 mol NaCl in 13 L H2O .36 mol Br2 in 83 mL H2O 52 g KOH in 601 mL 65 g Al(OH)3 in 253 mL

Molality (m) Useful for solid solutions Formula: Note: 1.0 kg H2O = 1.0 L H2O 1kg = 1000 g

Molality (cont) Find the molality for 6.3 mol KCl in 8.00 kg water Find molality for 16.1g Cl2 in 5000g of water Find the molality for 88 g NaOH in 520 g water Find the molality of 4.32 g Rb3PO4 in 0.65 L H2O

Essential Questions What are ppm and ppb and what are they used for? How do you calculate molarity? How do you calculate molality?

8.2 Tracked Assignment worksheet