Lesson Starter Write the stock system names for MnO, PbO 2 Write the stock system names for MnO, PbO 2 Manganese (II) Oxide Manganese (II) Oxide Lead (IV) Oxide Lead (IV) Oxide

How would you find the mass of the system if they could not measure it as a whole ?

Formula Weights and Percentage Composition Section 3.3

Three Concepts Formula Mass Formula Mass Molar Mass Molar Mass Percentage Composition Percentage Composition

Formula Mass The sum of the average atomic masses represented by the formula. The sum of the average atomic masses represented by the formula. H 2 0 as an example H 2 0 as an example 2 atoms of H 1 atom of O 1.01 amu x H atom = 2.02 amu amu x O atom = amu amu

Formula Mass NaCl NaCl H 2 SO 4 H 2 SO 4 MgCl 2 MgCl 2 HCl HCl amu amu amu amu amu amu amu amu

Molar Mass The mass in grams of 1 mole or x 1023 particles. (same number as formula mass) H20 as an example 2 moles of H 1 mole of O 1.01 g x H mole = 2.02 g g x O mole = g g/mol

Molar Mass NaCl NaCl H 2 SO 4 H 2 SO 4 MgCl 2 MgCl 2 HCl HCl g/mol g/mol g/mol g/mol g/mol g/mol g/mol g/mol

Percentage Composition (% Comp) The % by mass of each element in a compound. (FORMULA ON pg. 88) The % by mass of each element in a compound. (FORMULA ON pg. 88) Find the percentage composition of water. 2 moles of H 1 mole of O 1.01 g x H mole = 2.02 g g x O mole = g g/mol

Percentage Composition Find the percentage composition of water g H g O g H 2 O x 100% = 11.21% H g H 2 O x 100% = % O

Practice Find the percentage compositions of: Find the percentage compositions of: Ba(NO 3 ) 2 Ba(NO 3 ) 2 PbCl 2 PbCl 2

Ba(NO 3 ) 2 Ba(NO 3 ) 2 1 mol Ba X g/ mol Ba = g Ba 2 mol N X14.00 g/ mol N = g N 6 mol O X16.00 g/ mol O = g O g total

g Ba g N g O g total X 100 = g total X 100 = g total X 100 = 52.6 % Ba 10.7 % N 36.7 % O

PbCl 2 PbCl 2 1 mol Pb X207.2 g/ mol Pb = g Pb 2 mol Cl X35.45 g/ mol Cl = 70.9 g Cl g total

X 100 = 74.5 % Pb 25.5 % Cl g total g Pb 70.9 g Cl

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