Percent CompositionPercent Composition

The percent by mass of an element in a The percent by mass of an element in a compound is the number of grams of the compound is the number of grams of the element divided by the mass in grams of the element divided by the mass in grams of the compound multiplied by 100%.compound multiplied by 100%.

% Mass of element = mass of element/mass of % Mass of element = mass of element/mass of compound x 100%compound x 100%

% Mass = mass of element in 1 mol compound % Mass = mass of element in 1 mol compound / molar mass of compound x 100%/ molar mass of compound x 100%

Percent CompositionPercent Composition

A compound is formed when 9.03 g Mg A compound is formed when 9.03 g Mg combines completely with 3.48 g N. combines completely with 3.48 g N. What is the percent composition of this What is the percent composition of this compound?compound?

Percent CompositionPercent Composition

When 14.2 g sample of mercury (II) oxide When 14.2 g sample of mercury (II) oxide is decomposed into its elements by is decomposed into its elements by heating, 13.2 g Hg is obtained. What is heating, 13.2 g Hg is obtained. What is the percent composition of the the percent composition of the compound?compound?

Percent CompositionPercent Composition

Calculate the percent composition of Calculate the percent composition of these compounds:these compounds: Ethane ( CEthane ( C22HH66 ) )

Sodium hydrogen sulfate ( NaHSOSodium hydrogen sulfate ( NaHSO44 ) )

Percent CompositionPercent Composition

Calculate the percent nitrogen in these Calculate the percent nitrogen in these common fertilizers:common fertilizers: NHNH33

NHNH44NONO33

Empirical FormulaEmpirical Formula

The empirical formula of a compound The empirical formula of a compound shows the smallest whole-number ratio of shows the smallest whole-number ratio of the atom in the compound.the atom in the compound.

EX: COEX: CO22......... not C......... not C22OO4 (molecular formula)4 (molecular formula)

CH………not CCH………not C66HH6(molecular formula)6(molecular formula)

CHCH22O……not CO……not C66HH1212OO6(molecular formula)6(molecular formula)

Empirical Formula- Empirical Formula- STEPSSTEPS

Convert each percent to grams.Convert each percent to grams. Convert grams to moles of each elementConvert grams to moles of each element Divide by the lowest number of molesDivide by the lowest number of moles The whole numbers you get are the The whole numbers you get are the

subscripts in the formulasubscripts in the formula

Empirical FormulaEmpirical Formula

Calculate the empirical formula of each Calculate the empirical formula of each compound:compound: 94.1% O, 5.9% H94.1% O, 5.9% H 67.6% Hg, 10.8% S, 21.6% O67.6% Hg, 10.8% S, 21.6% O

Empirical FormulaEmpirical Formula

1,6 – diamionhexane is used to make 1,6 – diamionhexane is used to make nylon. What is the empirical formula of nylon. What is the empirical formula of this compound if it is 62.1% C, 13.8% H, this compound if it is 62.1% C, 13.8% H, and 24.1% N?and 24.1% N?

Molecular FormulaMolecular Formula

The molecular formula of a compound is The molecular formula of a compound is either the same as its experimentally either the same as its experimentally determined empirical formula, or it is a determined empirical formula, or it is a simple whole-number multiple of its simple whole-number multiple of its empirical formula.empirical formula.

EX: COEX: CO2 2 (empirical)(empirical) C C22OO4 4 (molecular formula)(molecular formula)

CH CH (empirical) (empirical) CC66HH6 6 (molecular formula)(molecular formula)

CHCH22O O (empirical) (empirical) CC66HH1212OO6 6 (molecular formula)(molecular formula)

Molecular Formula - Molecular Formula - STEPSSTEPS

Calculate the molar mass of the empirical Calculate the molar mass of the empirical formula givenformula given

Use the molar mass of the molecular Use the molar mass of the molecular formula that is given and divide by the formula that is given and divide by the empirical formula massempirical formula mass

This will provide you with the whole This will provide you with the whole number that you use to multiply each number that you use to multiply each element in the empirical formula byelement in the empirical formula by

Molecular FormulaMolecular Formula

Find the molecular formula of ethylene Find the molecular formula of ethylene glycol, which is used as antifreeze. The glycol, which is used as antifreeze. The molar mass is 62 g/mol and the empirical molar mass is 62 g/mol and the empirical formula is CHformula is CH33O.O.

Molecular FormulaMolecular Formula

Which pair of molecules has the same Which pair of molecules has the same empirical formula? :empirical formula? :

CC22HH44OO22, C, C66HH1212OO66

NaCrONaCrO44, Na, Na22CrCr22OO77