Empirical & Molecular Formulas

#1 find the empirical formula 40% carbon; 6.7% hydrogen; 53.3% oxygen Remember: Assume 100 g Use molar mass to find moles of each element Divide by smallest number of moles Multiply if necessary to get to two whole numbers CH2O

#3 empirical – don’t erase yet! 30.4% nitrogen; 69.6% oxygen NO2

#3, continued (molecular) If the compound in question 3 has a molar mass of 92 g/mol, what is the molecular formula? Remember: Find the mass of the empirical formula Divide the mass of the molecular formula (given) by the mass of the empirical formula to get the multiplier Multiply each subscript by the multiplier to get the molecular formula N2O4

#7 A compound with the following composition has a molar mass of 60.10 g/mol: 39.97% carbon; 13.41% hydrogen; 46.62% nitrogen. Find the molecular formula. C2H8N2

#8 polarity In a bond between phosphorous and chlorine, where do the electrons spend the most time? Near chlorine

#9 polarity Determine if the following bonds are polar or nonpolar: C – H C – O S – F S – Cl N – O nonpolar (3.1 – 3.5) C – H nonpolar (2.6 – 2.2) C – O polar (2.6 – 3.5) S – F polar (2.6 – 4.0) S – Cl polar (2.6 – 3.2)

#2 empirical 92.3% carbon; 7.7% hydrogen CH

#4 7.19% phosphorous; 92.81% bromine PBr5

#5 70.0% iron; 30.0% oxygen Fe2O3

#6 Naphthalene is a carbon and hydrogen containing compound often used in moth balls. The empirical formula is C5H4 and its molar mass is 128.16 g/mol. Find the molecular formula. C10H8