Return from Winter Break: Periodic Trends and Gases Quiz Guided Inquiry: Molarity

Warm Up SEE HAND OUT: About Winter Break Assignment SHOW ME : Cornell Notes for Chapters 7 and 10 TIME: 3 MINUTES WHEN DONE: Be ready to review questions from handout and turn in Guided Inquiry: Oxidation Numbers

Agenda Review Questions and Answers Mini-Quiz (only Multiple Choice) Molarity and Dilution Demonstration: Hot Ice Guided Inquiry: Molarity Homework: Lab Notebook Set Up - Conductimetric Titration and Gravimetric Determination of Precipitate

REVIEW THE FOLLOWING 7.1 pg 264 A-46 7.3 pg. 265 7.5 pg. 269 7.7 SECTION PRACTICE PROBLEM 2 WITH PG. NUMBER ANSWER KEY 7.1 pg 264 A-46 7.3 pg. 265 7.5 pg. 269 7.7 pg. 271 7.8 pg. 276 10.3 pg. 408 A-47 10.4 pgs. 408-412

Winter Break Quiz: Multiple Choice SPREAD OUT: One person per table WRITE: Name and Date on Answer Sheet (make sure to write capital letter) USE: Scratch Paper WHEN INSTRUCTED: Turn Over Quiz and Begin TIME: 35 MINUTES WHEN DONE: Reread your answers and make sure they are correct

MOLARITY and DILUTION

volume of solution in liters Molarity The quantity of solute in a solution can matter to a chemist. We call the amount dissolved its concentration. Molarity is one way to measure the concentration of a solution: moles of solute volume of solution in liters Molarity (M) =

Mixing a Solution To create a solution of a known molarity, weigh out a known mass (and, therefore, number of moles) of the solute. Then add solute to a volumetric flask, and add solvent to the line on the neck of the flask.

Molarity Check Which is more concentrated, a solution prepared by dissolving 21.0 grams of NaF in enough water to make 500 mL of solution, or a solution prepared dissolving 10.5 g of NaF in enough water to make 100 mL of solution? (Molar mass of NaF= 42.0 g/mol) 0.500 mol / 0.500 L = 1 M 0.250 mol / 0.1L = 2.5 M © 2015 Pearson Education, Inc.

Molarity Check What is the molar concentration of K+ ions in a 0.015 M solution of potassium carbonate? © 2015 Pearson Education, Inc.

Molarity Check What is the concentration of ammonia in a solution made by dissolving 3.75 grams of ammonia in 120.0 L of water? How many grams of Na2SO4are there in 15 mL of 0.50 M Na2SO4? How many mL of 0.50 M Na2SO4 solution are needed to provide 0.038 mol of this salt? © 2015 Pearson Education, Inc.

Dilution One can also dilute a more concentrated solution by using a pipet to deliver a volume of the solution to a new volumetric flask, and adding solvent to the line on the neck of the new flask.

Dilution The molarity of the new solution can be determined from the equation M1  V1 = M2  V2, where M1 and M2 are the molarity of the concentrated and dilute solutions, respectively, and V1 and V2 are the volumes of the two solutions.

Dilution: Check 1.75 mL 8.75 mL 48.6 mL 57.1 mL 28570 mL What volume of a 1.00 M stock solution of glucose must be used to make 500 mL of a 1.75 x 10-2 M glucose solution? 1.75 mL 8.75 mL 48.6 mL 57.1 mL 28570 mL

Using Molarities in Stoichiometric Calculations

Titration A titration is an analytical technique in which one can calculate the concentration of a solute in a solution.

Titration A solution of known concentration, called a standard solution, is used to determine the unknown concentration of another solution. The reaction is complete at the equivalence point.

Demonstration: Hot Ice 170 g of sodium acetate 30 mL of water What is the molarity?

Guided Inquiry: Molarity COMPLETE: Molarity Guided Inquiry WORK: Together USE: Notes and each other TIME: 15 MINUTES WHEN DONE: Turn into class box and begin reading pre-lab