Ch 5 Molar Mass

Molar Mass: the mass of 1 mole of certain substanecs/particles

Unit: g/mol

  • The molar mass of CO2 is 44g/mol. How many moles of O atoms in 88g of CO2?

88g CO2 x (1mol / 44g) x (2 O / 1 CO2) = 4

2 moles of CO2 in 88g

2 moles of O in 1 CO2 mol

  • 4 mol of O atoms

2 conversion factros

  • using molar mass, convert g to mol

  • then use chemical formula to get mol of an element in a compound

How to calculate molar mass?

CHeck periodic table and add

  • Al2(SO4)3

find mass on perdiodic table

  • Al = 26.8g/mol

  • S = 32.07g/mol

  • O = 16.00g/mol

add

  • 2 × 26.8g/mol +

  • 3 x ( 1 × 32.07 + 4 × 16.00 )

  • = 342.17g/mol

Molar mass of Cs2CO3?

  • 132.9×2 + 12.01 + 16×3

  • 325.8g/mol

number of formula units of Cs2CO3 in 7.5g Cs2CO3?

  • ( 1 mol / 325.8 g ) x (7.5 g / 1 ) x ( 6.022×10²³ / 1 mol)

  • = 1.4 × 10²2 of Cs2CO3

  • Avagadro’s number converts mols to real number

Mass of 1.2044 × 10²4 of CH4 molecules? 10²

  • 1×12.01 + 1.008×4 = molar mass of 16.042g/mol

  • 1.2044 × 10²4 * (1 mol/6.022×10²³) = 2mol

  • 2mol x 16g/mol = 32g

number of mcs → (NA) moles of mcs → (molar mass) mass of mcs → (density) volume