•EXAM #1 ANSWER KEY POSTED

•OWL:

•CHAPTER 4 PART 1 HOMEWORK

•EXAM GRADES POSTED (LEFT SIDE “COURSE GRADES” LINK)

Announcements

Solution Concentration

Solution Solute Solvent

Concentration Qualitative

Dilute Concentrated

Quantitative Molarity=# moles of solute per 1L of solution

What do goldfish have to do with concentration?

goldfishcupfoodbaby

goldfishxcupsfoodbaby 2010

2

Solution Concentration Examples

How many moles of NH3 are in 575mL of 0.12mol/L solution?

A 0.56M solution of NH3 contains 22 mol NH3. How many Liters of solution are there?

What you “have”Conversion

factor

What volume of a 0.23M solution of K2SO4 contains 0.50 moles?

1. 0.115L2. 0.115mL3. 2.174L4. 2.174mL

How would you make 250mL of 1.00M NH3 from 15M NH3?

1. Take 16.7mL of 15M NH3 and dilute it to 250mL with water

2. Take 60mL of 15M NH3 and dilute it to 250mL with water

3. Take 0.0167mL of 15M NH3 and dilute it to 250mL with water

4. Take 3.75mL of 15M NH3 and dilute it to 250mL with water

Stoichiometry in Solution

Grams or mL reactant A

Grams or mL reactant B

Moles reactant BMoles reactant A

Molar massor

Solution concentration

Molar massor

Solution concentration

Balanced equation

andStoichiometry

Titration Example- Part 1

GOAL: To determine the molar mass of an unknown acid (H2A)

H2A + 2NaOH Na2A + 2H2O

1. Standardizing an NaOH solution using a “primary standard”A solution of sodium hydroxide is “standardized” by titration using solid oxalic acid, H2C2O4, as the acid. It is found that 24.5 mL of the NaOH solution is needed to react completely with 2.05 g of oxalic acid. What is the concentration of the NaOH solution?H2C2O4(aq) + 2 NaOH 2 H2O(l) + Na2C2O4(aq)

Titration Example- Part 2

2. Determining the molar mass of an unknown diprotic acid

The NaOH solution above was used to titrate an acid of unknown formula, but known to be diprotic: H2A, where we don’t know what “A” is. A 1.046 gram sample of the unknown acid is titrated using 31.4 mL of the NaOH solution. What is the molar mass of H2A?

H2A(aq) + 2 NaOH 2 H2O(l) + Na2A(aq)