RowanKiraTalia Yikaalo FRONT OF ROOM Alain Keith Drishti Grace Ale Angel Juan Emma Ylana Wilson Michael Sophie Tina Fatima Maddie Marpha Alvin Adaiha Erik Mario

Do-NOW  Complete the graded do-now  You may use your notes, handouts  Do-now is SILENT and INDEPENDENT  Today’s do-now is graded for  COMPLETENESS  EFFORT  APPROPRIATE PARTICIPATION Objective: SWBAT convert between mass and moles of an element.

11/8/2010  Objective: SWBAT to calculate percent composition for a compound. SWBAT determine the percentage of water in a hydrate using laboratory techniques  Agenda: do-now, percent composition, lab-finding the percentage of water in a hydrate  Homework: Complete 10 more problems (INCLUDING #20-30 if you haven’t already) in packet in preparation for QUIZ TOMORROW. Review session/extra help in chem lab, 3:15-3:40 today.

On the quiz, you will be given this: # of Particles (atoms or molecules) Moles Mass (in grams) 1mole 6.02 x particles Molar mass* 1 mole Molar mass* 6.02 x particles 1 mole * Molar mass for an element is the atomic mass from the periodic table (in grams), molar mass for a compound is the sum of the atomic masses of each atom in that compound

PERCENT COMPOSITION AND DERIVING CHEMICAL FORMULAS

Percentage  the relative amount of one part compared to the whole  If I ate 2/3 of a pizza yesterday, what percentage did I eat?  Divide the part I ate by the whole (2 / 3) to get a decimal =.67  Multiply the decimal by 100 = 67  I ate 67% of the pizza

Percentage  If 6 of my 30 fish are blue, what percentage of my fish are blue?  6 / 30 =.2 .2 x 100 = 20%  If I got a 15/45 on my Chemistry test, what percentage did I get right?  15/45 =.33 .33 x 100 = 33%  Questions about calculating a percentage?

Percent Composition  the amount of a compound that is made up of a certain element – measured by MASS  Ex: What percentage of Carbon Monoxide is made up of Carbon?  First need to find mass of whole compound 12g + 16g = 28g  Now divide mass of the part (carbon) by the mass of the whole (carbon monoxide) 12g/28g = x 100 = 43% Carbon Monoxide is 43% carbon

Percent Composition  Ex 2 – what percentage of water is made up of hydrogen?  Total mass: (2 x 1g) + 16g = 18g  Part / whole: 2g/18g =.11 .11 x 100 = 11%  Water is 11% Hydrogen

Percent Composition  Ex 3 – what percentage of water is made up of oxygen?  Find total mass: (2 x 1g) + 16g = 18g  Part/whole : 16g/18g =.89 .89 x 100 = 89%  Water is 89% oxygen

Percent Composition  Ex 3: What is the percent composition of each element in dinitrogen trioxide? HINT – make sure they sum to 100%

Lab – water of hydration  Hydrate – An ionic compound that contains water molecules as part of its crystal structure  Naming/writing formulas  CaCl 2 2H 2 O – Calcium Chloride dihydrate  This is a compound where each molecule of calcium chloride is combined with 2 molecules of water in the crystal structure  The prefixes are the same as for naming compounds

Lab – water of hydration  Anyhdrous – The form of a hydrate-forming compound with NO water in its structure  Salt – An ionic compound

Lab – water of hydration  Objective: To determine the percentage of water in a hydrate, and to calculate the ratio of the number of moles of water to the number of moles of anhydrous salt molecules.  You will be removing the water from a hydrate and calculating how much water was in it and then using that value to calculate the formula for the compound  CuSO 4 ·XH 2 O(s)  CuSO 4 (s) + H 2 O(g)

Lab – water of hydration  Follow instructions carefully – you will be graded on the completion and correctness of your data  Goggles must be worn at all times  Procedure…  Be careful with hot plates and hot beakers – do not put hot beakers on the balance  Remember to mass your beaker and then to subtract it from all mass readings  Heat your compound until it is entirely white/light blue – and then a little more (don’t burn it)

RowanKira Talia Yikaalo FRONT OF ROOM Alain Emma Drishti Grace Sophie Juan Angel Keith Ylana Wilson Michael Ale Tina Fatima Maddie Marpha Alvin Erik MarioAdaiha The person who’s name is in BOLD is the only person who may leave his/her seat during this lab

Do-NOW  Put away everything except:  A pencil  A calculator  Your homework (to hand in) Objective: SWBAT convert between mass and moles of an element.

11/8/2010  Objective: SWBAT to demonstrate facility with various stoichiometric calculations  Agenda: quiz, work on lab packet from yesterday  Homework: Week 11 HW, #1-5, LAB PACKET DUE FRIDAY – see me if you need help!

QUIZ  DO NOT WRITE ON PERIODIC TABLE  Stoichiometry road map is yours to keep – use it to study for test. You will not be given this on the test.  What does it mean to show all work?  Write given, with unit, over one  Write a fractional conversion factor next to it  Show that units cancel  ALL VALUES MUST HAVE UNITS

Do-NOW  Complete the graded do-now  You may use your notes, handouts  Do-now is SILENT and INDEPENDENT Objective: SWBAT convert between mass and moles of an element.

11/7/2010  Objective: SWBAT to differentiate between empirical and molecular formula. SWBAT find the molecular formula given the empirical formula and the molar mass.  Agenda: do-now, notes, practice problems  Homework: Week 11 HW, #6-8, LAB PACKET DUE FRIDAY – see me if you need help!

Molecular Formula  Gives a complete list of all the atoms in a molecule  EX: H 2 O  2 atoms of H, 1 of O  EX: C 6 H 12 O 6  6 atoms of c, 12 of H, 6 of O

Empirical Formula  Just gives the lowest, whole number RATIO of elements in the compound  EX: Glucose (Molecular formula: C 6 H 12 O 6 )  Empirical Formula:  CH 2 O  EX: Water (Molecular formula: H 2 O)  Empirical Formula:  H 2 O

What is the empirical formula for each of the following?  H 2 O 2  CH 4  C 2 H 10  C 12 H 22 O 11

Finding Molecular formula  What is the molecular formula for a compound with the empirical formula HO and a molar mass of 34g?  STEP 1 – find the total mass of the empirical formula given to you  1g + 16g = 17g  STEP 2 – divide the molar mass from the problem by the mass of the empirical formula  34g / 17g = 2  STEP 3 – multiply each subscript in the emp. form by the number you just found H2O2H2O2

Ex 2  What is the molecular formula for a compound with the empirical formula CH 3 and a molar mass of 45g?  STEP 1 – find the total mass of the empirical formula given to you  12g + (1g x 3) = 15g  STEP 2 – divide the molar mass from the problem by the mass of the empirical formula  45g / 15g = 3  STEP 3 – multiply each subscript in the emp. form by the number you just found C3H9C3H9

Ex 3  What is the molecular formula for a compound with the empirical formula NO 2 and a molar mass of 138g?  14g + (16g x 3) = 46g  138g / 46g = 3 N3O6N3O6

 Homework: Week 11 HW, #6-8 LAB PACKET DUE FRIDAY – see me if you need help!

Do-NOW  Complete the graded do-now  You may use your notes, handouts  Do-now is SILENT and INDEPENDENT Objective: SWBAT convert between mass and moles of an element.

11/18/2010  Objective: SWBAT to write the empirical formula for a compound given laboratory data  Agenda: do-now, notes, practice problems LAST NEW MATERIAL BEFORE THANKSGIVING!!  Homework: LAB PACKET– see me if you need help! Make sure WK 11 #1-8 is finished and ready to go over tomorrow.  Extra Help – Today (Thursday) 3:15-4:15

Finding Empirical Formula in the Lab  When we do Analytical Chemistry in the lab, we can find values for the amount of a certain element in a compound  Like when we found the amount of water in CuSO 4 XH 2 O  We have a system for taking the values we get in the lab and figuring out the empirical formula

Determine the empirical formula for a compound that is 74.83% carbon and 50.34% hydrogen by mass STEP 1 - Pretend you have 100 grams of the substance, make the % values into numbers of grams 74.83g of carbon50.34g of hydrogen STEP 2 - Convert each mass value into moles 74.83g carbon x 1 mole. = 6.24 moles carbon 112 g carbon 50.34g hydrogen x 1 mole. = moles H 11 g hydrogen

Determine the empirical formula for a compound that is 74.83% carbon and 50.34% hydrogen by mass STEP 3 - Divide all mole values by smallest # of moles moles / 6.24 moles = moles / 6.24 moles = 1 STEP 4 - Use the resulting numbers as your subscripts  CH 8

Determine the empirical formula for a compound that is 37.41% carbon and 25.17% hydrogen by mass STEP 1 - Pretend you have 100 grams of the substance, make the % values into numbers of grams STEP 2 - Convert each mass value into moles STEP 3 - Divide all mole values by smallest # of moles STEP 4 - Use the resulting numbers as your subscripts

 Ascorbic acid is another name for Vitamin C. It is composed of 40.92% carbon, 4.58% hydrogen, and 54.50% oxygen, by mass. Determine the empirical formula for ascorbic acid. STEP 1 - Pretend you have 100 grams of the substance, make the % values into numbers of grams STEP 2 - Convert each mass value into moles STEP 3 - Divide all mole values by smallest # of moles STEP 4 - Use the resulting numbers as your subscripts

Finding Empirical Formula  Sometimes you won’t be given percentages, but values for each element out of a total value  Ex: what is the empirical formula for a compound where a 5g sample contains 1.2g Carbon and 3.8g of Nitrogen.  To solve: find the percentage of each element, then proceed as before  1.2g Carbon / 5 g =.24 x 100 = 24% Carbon  3.8g Nitrogen / 5g =.76 x 100 = 76% Nitrogen

 A 4.99 gram sample of a compound contains 1.52 grams of nitrogen atoms and 3.47 grams of oxygen atoms.

 A 16.67g sample contains11.66 g iron and 5.01 g oxygen. What is its empirical formula?

Homework  LAB PACKET  Make sure to have WK 11 #1-8 finished and ready to go over tomorrow. See me if you need help!

Do-NOW  Complete the graded do-now  You may use your notes, handouts  Do-now is SILENT and INDEPENDENT Objective: SWBAT convert between mass and moles of an element.

11/18/2010  Objective: SWBAT  Agenda: do-now,  Homework: Week 11 HW # 9-16 (17 as a bonus), Start preparing for test next WEDNESDAY