Lesson StarterLesson Starter

Write the stock system Write the stock system names for MnO, PbOnames for MnO, PbO22

Manganese (II) OxideManganese (II) OxideLead (IV) OxideLead (IV) Oxide

How would you find the How would you find the mass of the system if mass of the system if

they could not measure they could not measure it as a whole ?it as a whole ?

Formula Weights and Formula Weights and Percentage CompositionPercentage Composition

Section 3.3Section 3.3

Three ConceptsThree Concepts

Formula MassFormula MassMolar MassMolar MassPercentage CompositionPercentage Composition

Formula MassFormula Mass

The The sum of the average atomic masses sum of the average atomic masses represented by the formula.represented by the formula.

HH220 as an example0 as an example

2 atoms of H

1 atom of O

1.01 amuxH atom

= 2.02 amu

16.00 amuxO atom

= 16.00 amu

18.02 amu

Formula MassFormula Mass

NaClNaCl HH22SOSO44

MgClMgCl22

HClHCl

58.44 amu58.44 amu 98.09 amu98.09 amu 95.21 amu95.21 amu 36.46 amu36.46 amu

Molar MassMolar Mass

The The mass in grams of 1 mole or 6.022 x 10mass in grams of 1 mole or 6.022 x 102323 particles. (same number as formula mass)particles. (same number as formula mass)

HH220 as an example0 as an example

2 moles of H

1 mole of O

1.01 gxH mole

= 2.02 g

16.00 gxO mole

= 16.00 g

18.02 g/mol

Molar MassMolar Mass

NaClNaCl HH22SOSO44

MgClMgCl22

HClHCl

58.44 g/mol58.44 g/mol 98.09 g/mol98.09 g/mol 95.21 g/mol95.21 g/mol 36.46 g/mol36.46 g/mol

Percentage Composition Percentage Composition (% Comp)(% Comp)

The The % by mass of each element in a % by mass of each element in a compound. compound. (FORMULA ON pg. 88)(FORMULA ON pg. 88)

Find the percentage composition of water.

2 moles of H

1 mole of O

1.01 gxH mole

= 2.02 g

16.00 gxO mole

= 16.00 g

18.02 g/mol

Percentage CompositionPercentage Composition

Find the percentage composition of water.

2.02 g H

16.00 g O

18.02 g H2Ox 100% = 11.21% H

18.02 g H2Ox 100% = 88.79 % O

PracticePracticeFind the percentage Find the percentage compositions of:compositions of:

Ba(NOBa(NO33))22

PbClPbCl22

Ba(NOBa(NO33))221 mol Ba X 137.33 g/ mol Ba = 137.33 g Ba

2 mol N X 14.00 g/ mol N = 28.00 g N

6 mol O X 16.00 g/ mol O = 96.00 g O

261.33 g total

137.33 g Ba

28.00 g N

96.00 g O

261.33 g total X 100 =

261.33 g total X 100 =

261.33 g total X 100 =

52.6 % Ba

10.7 % N

36.7 % O

PbClPbCl221 mol Pb X 207.2 g/ mol Pb = 207.2 g Pb

2 mol Cl X 35.45 g/ mol Cl = 70.9 g Cl

278.1 g total

X 100 =

X 100 =

74.5 % Pb

25.5 % Cl

278.1 g total

278.1 g total

207.2 g Pb

70.9 g Cl

HomeworkHomework

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