Report

Formula Weight & Molecular Weight • The FORMULA WEIGHT of a compound equals the SUM of the atomic masses of the atoms in a formula. • If the formula is a molecular formula, the formula weight is also called the MOLECULAR WEIGHT. The MOLE • Amount of substance that contains an Avogadro’s number (6.02 x 10 23)of formula units. The MOLE • The mass of 1 mole of atoms, molecules or ions = the formula weight of that element or compound in grams. Ex. Mass of 1 mole of water is 18 grams so molar mass of water is 18 grams/mole. Formula for Mole Mole = mass of element formula weight of element Sample Mole Calculations 1 mole of C = 12.011 grams » 12.011 gm/mol • 0.5 mole of C = 6.055 grams » 12.011 gm/mol Avogadro’s Number • Way of counting atoms • Avogadro’s number 23 = 6.02 x 10 Point to Remember One mole of anything is 6.02 23 x 10 units of that substance. And…….. • 1 mole of C has the same number of atoms as one mole of any element Formula Weight & Molecular Weight • The FORMULA WEIGHT of a compound equals the SUM of the atomic masses of the atoms in a formula. • If the formula is a molecular formula, the formula weight is also called the MOLECULAR WEIGHT. Summary • Avogadro’s Number gives the number of particles or atoms in a given number of moles • 1 mole of anything = 6.02 x 10 atoms or particles 23 Sample Problem 2 • Compute the number of atoms and moles of atoms in a 10.0 gram sample of aluminum. Solution • PART I: • Formula for Mole: –Mole = mass of element atomic mass of element Solution (cont.) • Part II: atoms To determine # of • # atoms = moles x Avogadro’s number Problem # 2 • A diamond contains 5.0 x 1021 atoms of carbon. How many moles of carbon and how many grams of carbon are in this diamond? Molar Mass • Often referred to as molecular mass –Unit = gm/mole • Definition: –mass in grams of 1 mole of the compound Example Problem • Determine the Molar Mass of C6H12O6 Solution • Mass of 6 mole C = 6 x 12.01 = 72.06 g • Mass of 12 mole H = 12 x 1.008 = 12.096 g • Mass of 6 mole O = 6 x 16 = 96.00 g • Mass of 1 mole C6H12O6 180.16 g = Problem #3 • What is the molar mass of (NH4)3(PO4)? Molar Mass • Often referred to as molecular mass –Unit = gm/mole • Definition: –mass in grams of 1 mole of the compound Sample Problem • • • • • • • • • • Given 75.99 grams of (NH4)3(PO4), determine the ff: 1. Molar mass of the compound 2. # of moles of the compound 3. # of molecules of the compound 4. # of moles of N 5. # of moles of H 6. # of moles of O 7. # of atoms of N 8. # of atoms of H 9. # of atoms of O