Presentation on theme: "What does the little number below each"— Presentation transcript:
1 What does the little number below each Element mean?What are its’ units?amu/atom
2 one amu is defined as 1/12th What is an amuone amu is defined as 1/12thof12C
3 Average atomic mass or atomic weight is determined by a mass spectroscope. example: Analysis of a sample of carbon was found to have the following isotopes12C – %13C – %14C – %What is the atomic weight of Carbon
5 How high could you stack a mole of sheets of paper? How much is a mole?How high could you stack a mole of sheets of paper?
6 How much would a mole of iron weigh? Could you lift it? Look on the back inside cover for amu and molex 1023 atoms of Fe55.85 amux g*=55.85 g1atom of Fe1 amu
7 What is the Mole?One mole is equal to the number of carbon atoms in exactly grams of C-12: 6.02 x 1023 atoms
8 The Shopping Mole x g/ mole 22.4 L / mole # of atoms or molecules6.02 x atoms or molecules/moleMolex g/ mole22.4 L / moleMass of atomor moleculevolume of gasThe Shopping Mole
9 Calculate the numbers of atoms of cesium found in 3.57 moles of cesium Calculate the numbers of atoms of cesium found in 3.57grams of cesiumCalculate the mass of 4.82 x 1023 atoms of cesium
10 1. Calculate the mass of 4.65 moles of (NH4)2S Calculating the molar mass of a compound (NH4)2S1. Calculate the mass of 4.65 moles of (NH4)2S2. Calculate the numbers of atoms of nitrogen found in 3.57grams (NH4)2S3. Calculate the mass of nitrogen in 3.76 x 1024 formula units of (NH4)2S
11 Determining Percent Composition of Compounds Given the compound: Al(HPO3)3What are the percent compositions of each of the atoms from which the above compound is constructed?Mass of Aluminum= 1 mol Al26.9 grams= 26.9g Almole of AlMass of hydrogen = 3 mols H1.01 gram= Hmole of H266 gAl(HPO3)3Mass of Phosphorus = 3 mols P30.9 gram= g Pmole of PMass of oxygen = 9 mols O16.0 gram= 144 g Omole of P
12 10.1% Mass percent of Al: 1.13% Mass percent of H: 34.8% mass of Al26.9 g10.1%=x 100=Mass percent of Al:mass of Al(HPO3)3266 gmass of H3.03 gx 1001.13%=Mass percent of H:=mass of Al(HPO3)3266 gmass of P92.7 g34.8%x 100Mass percent of P:==mass of Al(HPO3)3266 gmass of O54.1%144 g==x 100Mass percent of O:266 gmass of Al(HPO3)3
13 Empirical formulaA compound is composed of Cl 71.65% and C 24.27% and H 4.07% what is the empirical formula? The Molar mass is 98.96g/mole, what is the molecular formula?
14 0.255 g isopropyl alcohol is combusted Determining the Empirical Formula of a Compound Using Combustion AnalysisCombustion Analysis0.255 g isopropyl alcohol is combustedmass difference of H2O absorber = gmass difference of CO2 absorber = g
15 mass difference of H2O absorber = 0.306 g mass difference of CO2 absorber = g1 mole CO212 g Cgrams of C: g CO2= 0.153g C44 g CO21 mole CO21 mole H2O2.02 g Hgrams of H: g H2O= g H18 g H2O1 mole H2Ograms of O: g g g H = g
16 Assume that the empirical formula for the compound is C3H8O 1 mol C1C: g C= 2.97= mol C12 g C0.00431 mol H1H: g H= 7.91= mol C0.00431.01 g H11 mol OO: g O= 1.00= mol O0.004316 g OAssume that the empirical formula for the compound is C3H8O
17 Ascorbic acid (Vitamin C) contains 40. 92 percent C, 4 Ascorbic acid (Vitamin C) contains percent C, 4.58 percent H, and percent O by mass. What is the empirical formula of ascorbic acid?Ethylene glycol, the substance used in automobile antifreeze, is composed of 48.7 % C, 9.7 percent H, and 51.6 percent O by mass. Its molar mass is62.1 g/mol. (a) What is the empirical formula of ethylene glycol? (b) What is the molecular formula
18 So What is Stoichiometry? mass of A in g mole 3(moles C) C g = mass CA g 1(moles A) mole1A + 2B → 3C + 4D
19 Na2SO3(aq) + 2AgNO3(aq) Ag2SO3(s) + 2NaNO3(aq) If 3.4 g of silver nitrate is mixed w/ excess sodium sulfite, what would be the theoretical yield for silver sulfite?in molesin formula unitsin L at STPin grams
20 Na2SO3(aq) + 2AgNO3(aq) Ag2SO3(s) + 2NaNO3(aq) If 3.4 g of silver nitrate is mixed sodium sulfite, how many grams of sodium sulfite would you need to react completely?
21 Na2SO3(aq) + 2AgNO3(aq) Ag2SO3(s) + 2NaNO3(aq) If 4.5 g of sodium sulfite is mixed w/ excess silver nitrate, what would be the theoretical yield for silver sulfite?What would be the percent yield if 4.1g was produced in the lab?
22 Na2SO3(aq) + 2AgNO3(aq) Ag2SO3(s) + 2NaNO3(aq) If 4.3 g of silver nitrate is mixed w/ 3.2g sodium sulfite, what would be the theoretical yield for silver sulfite?How much of the excess reagent is left over?
23 Using Stoichiometry in the Laboratory Na2SO3(aq) + 2AgNO3(aq) Ag2SO3(s) + 2NaNO3(aq)20 ml0.12 M20 ml0.35 M1. How many grams of silver sulfite would be produced?2. What would be the molarity of the sodium nitrate?