Good afternoon!Lot’s of things to pick up today:

Quiz ScantronQuiz version that you tookLab SheetFinal Study Guide Dry Erase BoardMarker

10 minutes to look over missed quiz questions & answer the Catalyst

pHTest Tube [H+] (mol/L) pH

1 0.01 <42 0.001 <43 0.0001 44 0.00001 55 0.000001 6

• How does the molarity of H+ change?• How does the pH change?• As the concentration of H+ increases, pH __________________.• Why are the pH’s for test tubes 1 and 2 indicated as “<4”?• What is an Arrhenius acid and base?• What is a Bronsted-Lowry acid and base?

(mm=119.02 g/mol)

pHpH is a scale used to reflect the concentration of

H+ ions! (but we really know that there are no free H+ ions, only hydronium (H30+)

Arrhenius acid is what? Bronsted-Lowry acid is what?

Remember that water is neutral:HOH <--> H+ + OH-

Example Brønsted Acids and Bases:

Here, H2O acts as a Brønsted acid by donating a proton to

NH3 which acts as a Brønsted base.

NH3 + HOH NH4+ + OH-

Neutralization ReactionA reaction between an acid and a base where enough

of each are combined so that the final solution is no longer acidic or basic, but neutral

What would be a product of a neutralization reaction?

We can use this fact to figure out the molarity of an acid or base solution with an unknown concentration by seeing how much of the other is required to neutralize it

TitrationDefinition◦ Analytical method

in which a standard solution is used to determine the concentration of an unknown solution.

standard solution

unknown solutionCourtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Buret

stopcock

Erlenmeyer flask

Titration VocabularyTitrant◦ The substance added to the analyte in a

titration (a standard solution)Analyte◦ The substance being analyzed

Equivalence point◦ The point in a titration at which the

quantity of titrant is exactly sufficient for stoichiometric reaction with the analyte.

Acid-Base Titration

Titrant

Analyte

If the concentration of the titrant is known, then the unknown concentration of the analyte can be determined.

Buret Reading

Acidic, basic, or neutral??

The “perfect pink” for a titration with phenolphthalein

Indicator - changes color to indicate pH change

Volume base added

Example… phenolphthalein is colorless in acid and pink in basic solution

pH

Endpoint =7

pink

point at which exactly enough reactant has been added for the solution to be neutralized and no more

Equivalence point (endpoint)Point at which equal

amounts of H3O+ and OH- are present in solution.

Determined by…indicator color changedramatic change in pH

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Titration

moles H3O+ = moles OH-

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

White Board Review!Water SolubilityMolarityDilutionsAcid and Base

Problem #1What mass of CaCl2 (mm=110.98 g/mol) is

required to make 1.25 L of a 0.250 M solution?

Answer: 34.7 g

Problem #2If 25 g of KCl is added to 50 g of water at 40°C, the solution would be:

1)Unsaturated2)Saturated3)Supersaturated

Problem #3What characteristic of compounds like sugar and

salt allow them to dissolve in water unlike oil?

Answer: they are polar, “like dissolves like”

Problem #4What volume of of a a 5.00M Ca(NO3)2 solution is

needed to prepare 465 mL of a 0.250 M Ca(NO3)2 solution?

Answer: 23.3 mL

Problem #5Calculate the molarity of a solution prepared by

dissolving 4.1 g of solid KBr (mm=119.02 g/mol) in enough water to make 1.10 L of solution

Answer: 0.031 M

Problem #6Classify the following as an acid or base:

H3PO4

NaOHCa(OH)2

H2S