Chemistry 116 Chapter 3 Notes ( Bangbo Yan)
Chemistry 116 Chapter 3 Notes ( Bangbo Yan) CHEM 116
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This 2 page Class Notes was uploaded by Jamisha Evans on Friday March 4, 2016. The Class Notes belongs to CHEM 116 at Western Kentucky University taught by Bangbo Yan in Spring 2016. Since its upload, it has received 14 views. For similar materials see INTRO TO COLLEGE CHEMISTRY in Chemistry at Western Kentucky University.
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Date Created: 03/04/16
Chemistry 116 chapter 3 Notes (Bangbo Yan) Molecular Mass • Sum of atomic masses of all atoms in molecule of substance • Unit: measured in amu EXAMPLE: Molecular mass of H 2O is 18.02 amu H 2 2 x 1.008= 2.016 amu O= 1 x16.00= 16.00 amu 18.02 amu (add 2.016 and 16.00; round to correct amt. of sigfigs) Formula Mass • Sum of atomic masses of all atoms in formula unit of the compound, whether molecular or not • Unit: measure in amu EXAMPLE: Formula mass of CaCl 2 is 110.98 Ca= 1 x 40.08= 70.40 amu Cl 2 2 x 35.45= 40.08 amu 110.98 amu ( add and round) The mole Concept • Mole: quantity of a given amount of substance that contains as many molecules or formula units as the number of atoms in exactly 12g of carbon-12 ♦ Symbol: mol ( no unit for mole; similar to when we say 1 pair of shoes or 12 dozen eggs, they are not measured in units) • Avogadro’s number: number of atoms in exactly 12g of carbon-12. Avogadro’s number is 6.022 x 103 • Molar mass: mass of one mole of substance. The molar mass in grams per mol is numerical equal to the formula mass in amu ♦ Unit: grams (g) EXAMPLE: 1 mol O= 16.00 g O= 16.00 amu (same but different unit) ♦ How to calculate the mass of one atom? 23 • Take the mass of the atom and divide it by the Avogadro’s number (6.022 x10 ) EXAMPLE: Mass in grams of one oxygen atom is 2.657 x 10 g -23 1 mol O= 6.022x 10 O atoms Mass of O= 16.00g 16.00g O/6.022 x 10 23O atoms= 2.657 x 10 g -23 ♦ How to calculate the mass of one molecule? • Take the mass of the entire the molecule (each atom in the molecule) and divide it by Avogadro’s number. -22 EXAMPLE: Mass in grams of a hydrogen bromide molecule is 1.343 x 10 g 23 1 mol of HBr= 6.022x 10 Mass of HBr= 80.91g 23 -22 80.91g HBr/ 6.022x 10 HBr atoms= 1.343x 10 g ♦ How to convert moles of substances to grams? • Take the amount of moles given and multiply it by the molar mass of the substance EXAMPLE: convert 0.721 mol of C 6H 12(g6ucose) to grams Molar mass of C H6O 12160.16g 0.721 mol x 180.16g=129.90