THE MOLE

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Molar Masses:

The _____ of the masses of all the elements in a chemical formula expressed in _____ unit per ______.

H2O 2(1 g/mol) + 16 g/mol = 18 g/mol

H2SO4 2(1 g/mol) + 32 g/mol + 4(16 g/mol) = 98 g/mol

Moe’s Mall: Map of finding masses, parts and volumes.

BULK FOOD STORE“Consume MASS quantities” Anything with gram units

Parts Store ‘Parts is Parts’ [atoms, ions, formula units, molecules, etc.]

Molar Mass of X: g/mol

[MOlEs]

Molar Volume of X:22.4 L /mol

Music Store ‘Turn up the VOLUME” [mL, L, etc]

Avogadro’s Number of X :6.02 x 1023

Sample Calculation: Mass(X) Mol(X)

g mol 50.4 g Ca Br2 = ? mol

50.4 g Ca Br2 x 1 mole = .252 mol

200 g CaBr2

Mass(X) (_____________________________) Mol(X)

Sample Calculation: Mol(X) Mass(X)

mol g 1.26 mol NaCl = ?g 1.26 x 58.5 g = 73.7 g 1 mol

Mol(X)(__________________________) Mass(X)

Sample Calculation: Number(X) Mass(X)

particles grams 7.74 x 1026 formula units of Al2O3 = ? g 7.74 x 1026 x 1 mol x 102 g = 1.31 x 105 g

6.02 x 1023 1 mol

Number(X) (_____________________) Mol(X) (______________) Mass(X)

PERCENT COMPOSITION

•It helps to know the ______________composition of the components in a shirt because they affect how warm it is, whether it will need to be ironed, and how it should be cleaned.

10.3

PERCENT COMPOSITION

In a chemical compound the percent composition determines the _______________of that compound

relative mass of each _________, or _________ of elements in relationship to the entire ________________

mass of __________ x 100 = % composition

mass of _____________

Percent Composition of a Compound

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

10.3

(ex) Mass Percents of Fe & O in Fe2O3

Mass of Fe 2 (55.8 ) = 111.6 amu Mass of O 3 (16.0) = 48.0 amu Mass of Fe2O3 159.6 amu ___________________________________ % Fe 111.6 amu x 100 70 %

159.6 amu % O 48.0 amu x 100 30 %

159.6 amu

EMPIRICAL FORMULAS

____________________ chemical formulas _________________ cannot be divided by a

common number (other than one).

CALCULATING EMPIRICAL FORMULAS 1] Determined using % composition data 2] % used as ________ and then converted

to ___________ 3] Divide by ____________ number of moles 4] If Necessary, ___________ to get Mole

ratios reduced to __________ numbers [subscripts]

Sample Calculation

Analysis shows water to be 88.8% oxygen and 11.2 % hydrogen by mass.

What is the empirical formula? In every 100 g sample:

88.8 g of O and 11.2 g of H.

Assuming a 100 g sample..Use Molar Masses: 88.8g = 5.55 moles O 11.2 g = 11.2 moles H

16.0 g/mol 1.0 g/mol Mole Ratio = 5.55 : 11.2, Divide both by 5.55

reduces to 1 O : 2 H ratio Used as the subscripts EF= H2O

MOLECULAR FORMULAS

Expresses the chemical formula as it actually exists in ______________.

Is the ____________ as, or a ___________ of the empirical formula.

Molecular Formulas10.3

methanal(CH2O),

ethanoic acid(C2H4O2), and glucose(C6H12O6)

all have the __________ empirical formula—CH2O.

CALCULATING MOLECULAR FORMULAS 1] Know, or be able to calculate the

___________ formula. 2] Know, or be given the ___________ mass 3] Divide _______________ mass by mass

of the ____________ formula 4] Multiply all __________________ by this

factor

Given: 92.3% C, 7.7% H, Molecular Mass of 26 g/mol

Calculate empirical formula 92.3 g = 7.69 moles C 7.7 g = 7.7 moles H

12.0 g/mol 1.0 g/mol 7.69 : 7.7 1 mol C: 1 mol H CH

empirical formula mass = 13 g/mol molecular mass = 26 g/mol [26 / 13= 2] Molecular Formula: CH x 2 = C2H2