Moles

The Mole 1 dozen = 12 1 mole = 6.02 x 1023 The mass of 1 mole of an element is the mass on the periodic table 1 mole of Hydrogen = 1 g of Hydrogen 1 mole of Helium = 4 g of Helium

Molar Mass Molar mass is the mass of 1 mole of a substance Units: g/mol The molar mass of an element is the mass number for the element that we find on the periodic table The molar mass of a compound is the mass of the elements in that compound added together. We have special terms for the molar mass of a compound.

} } Molar Mass Calculate the molar mass of NaCl: Na: 1 x 23 = 23 Cl: 1 x 35 = 35 Calculate the molar mass of Na(NO3)2: N: 2 x 14 = 28 O: 6 x 16 = 96 } = 58 g/mol } = 147 g/mol

Conversion Review What is a ratio? A comparison of two things which are equal to one another Remember how we use ratios to perform metric conversions: How many centimeters in 5 meters? 5 m x 100 cm = 500 cm 1 m

Conversions We use molar mass as a ratio for conversions Molar mass = g/mol We use Avogadro’s number as a ratio for conversions 6.02 x 1023 atoms, molecules / 1 mol

Conversions To convert from grams to moles: 12 g Helium x 1 mole Helium = 3 moles Helium 4 g Helium To convert from moles to atoms: 3 moles He x 6.02 x 1023 atoms He = 1.81 x 1023 atoms He 1 mole He

Conversion Review Remember when converting between two units with prefixes we used two ratios. We always go through the base unit: How many kilometers in 500 centimeters? 500 cm x 1 meter x 1 kilometer = 0.005 km 100 cm 1000 m

Conversions To convert from grams to atoms we use two ratios Just like we go through the base unit for two- step metric conversions, we go through the mole for two-step mole conversions

conversions To convert from grams to atoms: 16 g He x 1 mole He x 6.02 x 1023 atoms He = 2.41 x 1023 4 g He 1 mole He atoms He To convert from atoms to grams: 3.5 x 1023 x 1 mole He x 4 g He = 2.33 g atoms He 6.02 x 1023 atoms He 1 mole He