Concentrations Express the concentrations of solutions in terms of percent by mass, percent by...

Concentrations Express the concentrations of solutions in terms of percent by mass, percent by volume, parts per million

and molarity. Use Table T to calculate problems relating to

concentrations. Describe the preparation of a solution given the

molarity.

Aim How can we use mathematics to understand the

concentrations of solutes?

Essential Questions:

1. In what ways can we describe the concentrations of solutions?

2. How can we use reference Table T to calculate parts per million and molarity?

3. How do we describe the preparation of a solution, given the molarity? Explain.

Key Words

solute, solvent,

dilute, percent by

volume, percent by

mass, parts per

million and

molarity.

Picture ThisYou are in a lab and your petri dish broke, spreading cultured bacteria all over the table!

You head over to the supply closet to get some alcohol so you can clean up and destroy the bacteria before they spread.

2 % 90 %

Which bottle would you take?

What do the percentages represent?

When it Comes to Solutions,

Concentration is Important!If you are going for a surgery, you would want your anesthesiologist to administer the appropriate concentration of anesthesia to you!

If you are going for a swim at an indoor pool, you would want the maintenance crew to mix the appropriate concentration of chlorine in the pool. Too much and your hair may fall out. Too little and you may be swimming in bacteria!

We are going to spend the next two lessons discussing the different ways concentration can

be represented in a solution.

Sneak Peak

Percent by Mass

Percent by Volume

Parts Per Million

Molarity

What is the Formula for Calculating Percentages?

Using terms such as “part” and “whole,” please write down the generic formula for

calculating percent.

Percent Concentration Formulas

Mass Percent Concentration

Volume Percent Concentration

Practice1. A student dissolves 25.0 grams of glucose in

475 grams of water. What is the mass percent concentration of the glucose solution?

Practice

2. A solution is prepared by dissolving 90 milliliters of pure hydrogen peroxide in enough water to make 3000 milliliters of solution. What is the volume percent concentration of the hydrogen peroxide solution?

What if I need to know the concentration of a very dilute substance whose

concentration turns out to be a tiny fraction of a

percent?

POISONOUS MATERIAL

• H2S?

• DISSOLVED OXYGEN IN WATER

Parts per MillionParts per Million (ppm)

Scientists express the maximum allowable concentrations of toxic or cancer-causing substances in ppm.

Ex. The maximum allowable concentration of arsenic in drinking water is 0.05 ppm, which means 5 grams of arsenic per 100,000,000 grams of drinking water.

Practice

1. A certain gas has a concentration in water of 2 grams per 100 kilograms of water. What is the concentration of the gas in parts per million?

III. Concentration CalculationsA. The concentration of a solution may be

expressed as

A. Percent by Mass

a. Percent by Volume

b. Parts per Million (ppm)

c. Molarity (M)

Notes