Study Guides (251,533)
US (124,855)
Mizzou (1,028)
CHEM (38)
CHEM 1320 (22)
Ganley (10)

Chem-Chpater 3.docx

13 Pages

Course Code
CHEM 1320

This preview shows pages 1-3. Sign up to view the full 13 pages of the document.
Chapter 3: Stoichiometry of Formulas and Equations  Mass Relationships in Chemical Reactions 8/28 Microscopic: atoms and molecules Macroscopic: grams Atomic mass: mass of an atom in amu Carbon=12.01amu Hydrogen=1.008amu Oxygen=16amu Average atomic mass: on other page Mole (mol): Contains as many particles as there are atoms in 12  grams of 12C 1mol=N A=6.022x10^23  How big is a mole? Large burger chain: How long to serve a mole of hamburgers? 6.022x10^23 hamburgers  ­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­  = 1.67x10^14 3.6x10^9 hamburgers/day                                                 =458 billion  years! Counting objects of fixed relative mass: 12 apples @ 7g each=84g 12 oranges @4g each=48g 55.85gFe=6.022x10^23 atoms of Fe 32.07gS=6.022x10^23 atoms of S 1 12C atom                     12.00amu                 1.66x10^­24g ­­­­­­­­­­­­­­­    x   ­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­   =   ­­­­­­­­­­­­­­­­­­­­­­­   12.00amu          6.022x10^23 12C atoms                  1amu 1amu=1.66x10^­24 or 1 g=6.022x10^23amu conversion table=molar mass in g/mol Molecular mass (or molecular weight) is the sum of the atomic  masses (in amu) in a molecule SO2: 1S=32.07amu 1O=16.00amux2 ­­­­­­­­­­­­­­­­­­­­­­­­ SO2=64.07amu For any molecule: molecular mass (amu)=Molar mass (grams) Table 3.1 How many atoms are in 0.551 g of K? 1mol K=39.10g K 1mol K=6.022x10^23 atoms K 0.551 g K         1 mol K              6.022x10^23 atoms K                      x  ­­­­­­­­­­­­­­­  x  ­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­  =                             39.10 g K                    1 mol K =8.49x10^21 atoms K   How many H atoms are in 72.5 g of C3H8O? 1 mol C3H8O=(3x12) + (8x1) +16=60 g C3H8O 1 mol C3H8O molecules=8 mol H atoms 1 mol H=6.002x10^23 atoms H 72.5C3H8O  1mol C3H8O  8 mol H atoms  6.022x10^23 Hatoms                       x ­­­­­­­­­­­­­­  x  ­­­­­­­­­­­­­­­   x   ­­­­­­­­­­­­­­­­­­­­­­­­ =                          60g C3H8O     1mol C3H8O         1mol H atoms 5.82x10^24H atoms 8/30 Formula mass is the sum of the atomic masses (in amu) in a  formula unit of an ionic compound. 1Na=22.99amu + 1Cl=35.45amu = Nacl=55.44amu For any ionic compound, formula mass (amu)=molar mass (grams) 1 formula unit NaCl=58.44 amu 1 mole NaCl=58.44 g mol Formula mass of Ca3(PO4)2 ? 3Ca=3x40.08amu + 2P=2x30.97amu + 8O=8x16.00amu = Ca3(PH4)2=310.18amu Molar mass: 310.18 g mol Percent composition (by mass) 1 mole of CO weighs 28.01 g 12.01 g from C, 16.00 g from O 12.01/28.01x100%=42.88%Carbon 16.00/28.01x100%=57.12%Oxygen Percent composition of an element= n X molar mass of element  ­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­     X 100% molar mass of compound n is the number of moles of the element in 1 mole of the compound C2H6O % of Carbon=  2x12.01g/46.07gx100%=52.14% of Carbon % of Hydrogen= 6x1.008g/46.07gx100%=13.13% of Hydrogen % of Oxygen= 1x16.00g/46.07gx100%=34.73% of Oxygen All equal 100% A compound has a molar mass of 182.17g/mol. By mass, the  compound is 39.56% carbon, 7.74% hydrogen, and 52.70%  oxygen. What is the molecular formula? C6H14O6 Assume 1 mol 182.17g Q   39.56g Carbon           1 mol C                   x  ­­­­­­­­­­­­­­­­­­­  x   ­­­­­­­­­­­­­­­  =   6                           100g Q                    12.01 g C 182.17g Q     7.74g Hydrogen         1 mol H                   x    ­­­­­­­­­­­­­­­­­­­    x   ­­­­­­­­­­­­­­­  =   14                               100g Q                     1.008 g H 182.17g Q     52.70 g Oxygen          1 mol O                  x      ­­­­­­­­­­­­­­­­­­­  x   ­­­­­­­­­­­­­­­  =   6                                100g Q                    16.00 g O Book: assume 100gQ m 39.56gC 1mol/12.01g=3.294mol C/3.294=1 mol Cx3=3 7.74gH 1 mol/1.008g=7.68mol H=2.33 mol Hx3=7 52.70gO 1 mol/16.00g=3.294mol O=1 mol Ox3=3 Ratio: divide by the smallest number, then multiple by fraction C3H7O3 C­3x120.01=36.05 H­7x1.008=7.056 O­3x16.00=48.00 ­­­­­­­­­­­­­­­­­­­­­­­ 91.09 182.17/91.09=2 Now multiple the formula by 2 Ethanol contains only C, H, and O Combust 11.5 g ethanol Collect 22.0g CO2 and 13.5g H20 What is the empirical formula? Need to know grams and moles of C, H, O g CO2­­­m ▯ ol CO2­­­m▯ ol C­­­g▯  C 22.0 g CO2 x     1 mol CO2              1 mol C      ­­­­­­­­­­­­­­­­­­­  x  ­­­­­­­­­­­­­­=0.500 mol C       44.01 g CO2          1 mol CO2 0.500 mol C         12.01g C                         x  ­­­­­­­­­­­­­­­­  =6.01g C                                      mol C g H2O­­­m ▯ ol H2O­­­m ▯ ol H­­­▯  H 13.5 g H2O x     1 mol H2O              2 mol H      ­­­­­­­­­­­­­­­­­­­  x  ­­­­­­­­­­­­­­=1.50 mol H       18.02 g H2O          1 mol H2O 1.50 mol H         1.008 g H                         x  ­­­­­­­­­­­­­­­­  =1.51 g H                                      mol H g of O=g of sample­(g of C + g of H) 11.5 ethanol ­ (6.01g C + 1.51 g H) = 4.0 g O 4.0 g O          1 mol O                x  ­­­­­­­­­­­­­­­­  =0.25 mol O                        16.00 g O Mol C:0.500 Mol H:1.50 Mol O:0.25 Empirical=C0.5H1.5O0.25 Divide by smallest subscript (0.25) Empirical formula C2H6O 9/4 Constitutional Isomers of C2H6O Property                   Ethanol              Dimethyl Ether M  46.07 46.07 Boiling point 78.5 C ­25C Density @ 20C 0.789 g/mL liquid 0.00195 g/mL gas Structural          H     H  
More Less
Unlock Document
Subscribers Only

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

Unlock Document
Subscribers Only
You're Reading a Preview

Unlock to view full version

Unlock Document
Subscribers Only

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.