Catalyst – May 7-4, 2010

Monday Mystery Element

1. f-block element2. Named for an 1801

asteroid Ceres3. Its oxide is used to

coat walls of self-cleaning ovens

Catalyst – May 7-4, 2010

Monday Mystery Element

1. f-block element2. Named for an 1801

asteroid Ceres3. Its oxide is used to

coat walls of self-cleaning ovens

CERIUM!

Agenda

Mystery Element Finish test from before spring break On to the next one-molarity Molality Grams calculations Exit Question

Solutions

The Solute : the substance dissolved in the solution

The Solvent: the dissolving medium in the solution

Key Point #1: There are two main parts to a solution.

Solutions

Let’s consider an example:

Solute:

Solvent:

Solutions

Let’s consider an example:

Solute: Gatorade mix

Solvent:

Solutions

Let’s consider an example:

Solute: Gatorade mix

Solvent: Water

Solutions

Solutions come in different concentrations, which we measure in

molarity (M).

M =

Solutions

Solutions come in different concentrations, which we measure in

molarity (M).

M = Moles of solute

Liters of solution

* MUST BE IN MOLES OR LITERS, IF YOU HAVE MILLILITERS YOU MUST CONVERT! (COUGH, COUGH)

Example

What is the molarity of a solution that has 0.5 moles of lithium hydroxide (LiOH) dissolved in 1.0 L of water?

You do- whiteboards

What is the molarity of a solution that has 5 moles of barium bromide (BaBr2) dissolved in 2.0 L of solution?

Example

What is the molarity of a solution that has 0.25 moles of calcium sulfide (CaS) dissolved in 500 mL of solution?

WHAT DO YOU NOTICE???

You do- whiteboards

What is the molarity of a solution that has .88 moles of calcium oxide (CaO) dissolved in 300 mL of solution?

Example

How many grams of potassium chloride (KCl) are required to make 2.0 L of a 3.0 M solution?

WHAT DO YOU NOTICE?

EASY! Just convert moles to grams- you know how to do that!!

Molality

Key Point #2: For chemists, molality expresses another form of concentration -

similar to molarity.

m = Moles of solute

Kg of solventIt is the same thing, but instead of L on the bottom, it is kilograms on the bottom! Tomorrow!

Molality

You mix 100 moles of HBr into 10 kg of Br, what is your molality?

Molality

If you mix together 15 mol of solute and 5 kg of solvent, what is your molality?

Rally-Coach- TEAMWORK!!

After this announcement, you will find 1 partner in the class.

One person will be writing ONLY what the coach tells them to write. If you think the coach is wrong, you can hint to them that its not.

One person will be coaching them through the problem.

After each problem, you switch roles! If you finish, see me for extra credit.

Exit Question

How many grams of NaCl would it take make 2L of a 4M solution?

If you have 3.5 moles of NaCl in 2.2 L of water, what is the molarity?