Composition Stoichiometry blank 3.3.13.notebook Due: Ch 10 RG Hummmm... How do you "measure" bananas? > How many? Count 1 dozen naners or 12 naners Composion Stoichiometry 3 new conversion factors > Avogadro's constant > How much? Mass 1 lb of naners or 400 grams > Molar mass > What volume? 1 bushel of naners 1000 ml But in chemistry, "things" are sooo small it would be crazy to count them all, therefore, we have a new unit to tell amount (The MOLE!) > Molar volume of a gas > we still use grams and ml or L though Mar 3 9:42 AM 1. The Mole Counting by weighing The SI unit for the amount of a substance 1 mole = 6.022 x 1023 particles (Avogadro s number) Definition of the mole will allows us to convert between and Representative particles: species present in a substance ~ atom- refers to ELEMENTS (Fe is composed of Fe atoms) ~ molecule- refers to COVALENT CMPDS (water and DIATOMIC MOLECULES too) ~ Formula units refers to IONIC CMPDS (NaCl) Mar 6 6:20 PM 1
2. The Gram to Mole Link: Molar mass The mass of 1 mole of any compound or element is the molar mass. It is numerically equivalent to the atomic mass on the periodic table. Molar mass says that 1 mole of atoms weighs in grams as much as one average atom weighs in amu. So if 1 average atom of carbon has an atomic mass of 12.01 amu, one mole of carbon atoms has a molar mass of 12.01 grams. Verify: What is the mass of one mole of carbon atoms expressed in grams? (1 amu= 1.67 x 10-24 g) > So the mass of 1 mole of sulfur is > How many atoms are in 55.8 g of Fe? > If I wanted 6.02 x10 23 atoms of carbon, what mass of carbon would I need? > This is just a new equivalency that is different for every cmpd or element. Use it as a fraction/ conversion factor! Molar mass of compounds: H 2 O NaCl C 2 H 6 Mg(NO3)2 N 2 O 5 Mar 3 10:14 AM Examples: SHOW WORK with "unknown" and "given" 1.) 2.80 x 10 24 atoms of silicon to mole 2.) 0.32 mol of potassium to grams Molar Volume 1 mole of any GAS occupies a volume of 22.4 L at STP (standard temperature 273K and pressure 1 atm) 1 mole = 22.4 L 3.) 1.14 mol SO 3 to atoms oxygen 4.) 4.52 x 10 3 mol sodium phosphate to grams 5.) 2.5 x 10 2 liters carbon dioxide to atoms O 6.) 1.91 X 10 21 formula units lead(ii) iodide to grams 2
You Practice: Convert the following using avagadro s number, molar mass, and molar volume or a combination of the three. 1. 10.0 mol of chromium ( III) oxide to grams. 2. 3.32 mol K to grams 3. 4.6 x 10-25 molecules of carbon tetrachloride to grams. Moles of Chalk Lab Calcium carbonate Mass a piece of ordinary chalk and then write your NAME, I LOVE CHEMISTRY, YOUR FAVORITE CMPD, etc on the sidewalk. Weigh the chalk again, and determine the number of moles of calcium carbonate that were used. You must have a partner! Only 6 mins outside :) 4. 5.08 mol calcium nitrate to grams Weight of chalk before writing : Weight of chalk after writing : 5. 0.876 mol N2 gas to liters 6. 4.54 g of carbon dioxide into liters Grams of chalk required to write your name: Moles of chalk required to write your name: SHOW YOUR WORK! 7. 0.160 mole hydrogen peroxide to grams of oxygen 8. 0.75 moles barium chloride into grams. Mar 3 10:06 AM Mar 3 10:09 AM Complete some of PS 10!! WU: Percent Composion Without talking; perform the following tasks: Calculate the percent girls in the classroom: If there are 100 students, how many would be girls? If there are 234 students in the class how many would be girls? If there are 80 girls in the class, how big is the class? Mar 3 10:19 AM 3
To Calculate percent composition Student Practice KMnO 4 (NH 4 ) 3 PO 4 HCl Al 2 (SO 4 ) 3 K = N = H = Al = Calculate the percent composition of magnesium phosphate. If you have a 54g sample of magnesium phosphate, how many grams of that are oxygen? Mn = H = Cl = S = O = P = O = O = Mg(NO 3) 2 Calculate the percent composition of water in the following compound in zinc nitrate tetrahydrate Mg = N = O = Mar 3 10:31 AM Percent Composion of a Hydrate Lab all data should be collected today!! Solve the following Problems: 1. How many grams of oxygen can be produced for the decomposition of 100.g of potassium chlorate (KClO3)? 2. How much iron can be recovered from 25.0 g of Fe2O3? 3. How much silver can be produced from 125g of Ag2S? Materials: Goggles and Aprons! Electronic Balance Copper(II) sulfate 100 ml beaker ring stand with ring clamp crucible with lid and clay triangle weigh boat scoopula bunsen burner striker Magnesium sulfate Mar 5 6:34 PM Mar 3 10:19 AM 4
Empirical And Molecular Formula Empirical Formula the smallest whole number ratio of elements in a compound Label as empirical or molecular. For the empirical formulas suggest possible molecular formulas. For the molecular formulas, write the empirical formula. > C 4HO 2 > Ex. H 2O 2 has the empirical formula : > The empirical formula for C 6H 12O 6 is : > All ionic formulas are empirical > C 22H 44O 11 > CH 4 Molecular Formulas > True formula- how the molecule actually exists > It is a whole number multiple of the empirical formula > CaSO 4 > Hg 2Cl 2 Steps to calculate empirical formula 1. Convert amounts of all substance to moles Examples: Calculate the empirical formula for the following compounds: 1. 94.1%O, 5.9% H 2. To get the simplest rao, divide all moles by the smallest moles 3. If these numbers are round able, round to the nearest whole number and make them the subscripts in the formula. 1. (if there is a.5 then mulply by 2 to get a round able whole number) 2. A 0.858 sample of an unknown substance is found to contain 0.321g of fluorine, what is the empirical formula 5
Molecular formula To calculate: (Empirical Formula) n n = 2) The empirical formula is C 2H 4S with a molar mass of 179 g/mol. What is the molecular formula? 3. ) A 0.400 g sample of white powder contains 0.141 g potassium 0.115 g of sulfur, the remainder being oxygen. The experimental molar mass is 859.00 g/ mol what is the molecular formula for the compound? Mar 3 10:42 AM 6
Student Practice: Determine the Empirical Formula: 1. 52.7% potassium and 47.3 chlorine 2. 22.1% aluminum, 25.4% phosphorus, and 52.5% oxygen 3. 13% magnesium and 87% bromine 4. 32.4% sodium, 22.4 % sulfur, 45.1% oxygen 5. 25.3 % copper, 12.9 % sulfur, 25.7 % oxygen, and 36.1% water BIG QUIZ tomorrow on Compositional Chemistry (molar mass calculations, conversion from moles to rep particles or liters at STP, percent composition, and EF/MF). Determine the molecular formula: 1. The empirical formula of a compound is NO2. Its molecular mass 92g/mol. 2. The empirical formula of a compound is CH2. Its molecular mass is 70g/mol. 3. A compound is 40.0% carbon, 6.7% hydrogen, and the rest oxygen. Its molecular mass is 60.0g/mol. 4. A compound is 64.9%C, 13.5%H and the rest oxygen. Its molecular mass is 74 g/mol. What is its molecular formula? 5. A compound is 54.5 % carbon 9.1% hydrogen and the rest oxygen. Its molecular mass is 88 g/mol. What is its molecular formula? Mar 3 10:52 AM Oct 6 11:22 AM WU:?s on PS 10 (leave EF/MF work on desk during your lab please!) List the differences between copper (I) sulfate and copper (II) sulfate? PS 10? Lecture Notes with Student Practice complete? Part 1 of Copper Lab today Quiz on EF, MF, and Percent Comp after Lab Part 2 of the Lab will be completed tomorrow so please make sure you have all data so it can be turned in tomorrow!! If I had 100 g of each of these cmpds, what would this equate to in moles for each? HW: RG 11, Equation Writing HW Mar 3 11:25 AM Mar 3 11:27 AM 7
WU: Equation Writing HW and RG 11 Questions Replace the words with the appropriate symbols (pages 322,323 in your book) solid Forms, produces, yields liquid gas Reaction is heated Reaction required a catalyst of MnO2 Determining the Charge of Copper Lab You will be determining the charge of copper with from a given sample. Use your knowledge of empirical formulas! Be careful, as copper can get on clothes. Must use ONLY 50 ml of 0.160M CuCl x soln really swish the zinc w/o breaking anything or making a mess! use as least 6M HCl as possible... when using squirt boles, be careful and esmate ml... be careful! give me the "used" mossy zinc back :) share wash boles please! filter paper in ring stand or in smaller beaker that will hold it. Aqueous or a solution of precipitate Replace the words with the appropriate symbols and formulas for each compound. Ex. When solid iron is mixed with solid sulfur and heated, solid iron (III) sulfide is formed. Fe(s) + S(s) Fe2S3 (s) 1. When solid zinc is added to a solution of copper (II) sulfate, aqueous zinc sulfate and a precipitate of copper are formed. 2. When solid magnesium chlorate is heated, solid magnesium chloride and gaseous oxygen is formed. 3. Solid sulfur reacts with oxygen gas to form gaseous sulfur trioxide. 4. Solutions of silver nitrate and sodium bromide react to form aqueous sodium nitrate and a precipitate of silver bromide. 5. When electricity is applied to liquid water, it decomposes into hydrogen gas and oxygen gas. 6. Mercury(II) oxide is heated to produce solid mercury and gaseous oxygen. 7. Aqueous potassium iodide and aqueous lead(ii) nitrate react to produce solid lead(ii) iodide and a solution of potassium nitrate. 8. Solid aluminum reacts with oxygen gas to form solid aluminum oxide. 9. Aqueous magnesium chloride and aqueous ammonium nitrate react to form aqueous magnesium nitrate and ammonium chloride gas. 10. In the presence of manganese (IV) oxide, phosphorus and oxygen will react to form phosphorus pentoxide. Mar 3 10:42 AM Mar 11 6:58 PM MythBusters Partnerships Established now must discuss an idea for project by Tuesday!!! Oct 6 11:25 AM 8