Chemical Formulas: Chemical Formulas:

Formula MassFormula Mass& &

Molar MassMolar Mass

Subscripts in Chemical Subscripts in Chemical FormulasFormulas

subscripts show # atoms of each subscripts show # atoms of each element element

in in representative unitrepresentative unit

subscripts after parentheses refer to subscripts after parentheses refer to everything inside ( )everything inside ( )

Molar mass of an elementMolar mass of an element molar mass is mass (in grams) of 1 mole molar mass is mass (in grams) of 1 mole

of any pure substanceof any pure substance

molar mass of element is: molar mass of element is: numerically equal to atomic mass, but … numerically equal to atomic mass, but …

units change from amu to grams per mole units change from amu to grams per mole (g/mol)(g/mol)

Molar mass of elementsMolar mass of elements

Na has atomic mass of 22.98977 Na has atomic mass of 22.98977 amuamu molar mass = 22.98977 molar mass = 22.98977 grams/molgrams/mol

K has atomic mass of 39.0983 K has atomic mass of 39.0983 amuamu molar mass = 39.0983 molar mass = 39.0983 grams/molgrams/mol

Ca has atomic mass of 40.08 Ca has atomic mass of 40.08 amuamu so so molar mass = 40.08 molar mass = 40.08 grams/molgrams/mol

Round masses to whole number

Na = 22.98977 gramsrounds to 23g

K = 39.0983 grams rounds to 39g

Ca = 40.08 gramsCa = 40.08 grams rounds to 40grounds to 40g

Molar MassMolar Mass

MOLAR mass: always refers to mass in MOLAR mass: always refers to mass in grams per mole (g/mol)grams per mole (g/mol)

formula mass (FM) or gram formula mass formula mass (FM) or gram formula mass (GFM): (GFM): refers to mass in grams (g)refers to mass in grams (g) for amounts other than one mole for amounts other than one mole

Mole to Mass conversionsMole to Mass conversions

use PT for conversions involving use PT for conversions involving massmass

unless you want to memorize the unless you want to memorize the masses of all the elements!!masses of all the elements!!

Molar Mass ofMolar Mass of CompoundsCompounds = to sum of masses of all atoms in compound's = to sum of masses of all atoms in compound's

formulaformula

round atomic masses to whole number round atomic masses to whole number

ex: Hex: H22OO 2 H’s = 2 x 1g = 2g2 H’s = 2 x 1g = 2g 1 O = 1 x 16g = 16g1 O = 1 x 16g = 16g

FM of HFM of H22O is sum: 2g + 16g = 18gO is sum: 2g + 16g = 18g molar mass of Hmolar mass of H22O is 18g/molO is 18g/mol

Molar Mass of CompoundsMolar Mass of CompoundsCHCH44

1 C = 1 x 12g = 12g1 C = 1 x 12g = 12g 4 H’s = 4 x 1g = 4g4 H’s = 4 x 1g = 4g

FM is sum = 4g + 12g = 16gFM is sum = 4g + 12g = 16gmolar mass is 16g/molmolar mass is 16g/mol

challenge: find FM of

CuSO4•5H2O

4Ba3(PO4)2