A compound will have the same composition by mass.

Slide 1

A compound will have the same composition by mass.1

Calculate the following percentage by mass:percent = portion/total x 100

If two samples are the same substance, they should have the same percent composition by mass.2

A compound will have the same physical and chemical characteristics.3

Do the have the same percent composition? Are they the same compound?4

5Mass RatioPercent Composition of compounds was used to determine the MASS RATIO between elements.

Regardless of number of atoms, the MASS RATIO is the same.6carbon-12The standard for mass was arbitrarily chosen to be one atom of carbon-12

the MASS RATIO between elements was then used to calculate others.

The mass of one carbon-12 atom was set at 12 (exactly) amu.

amu is an arbitrarily chosen amount.7ATOMIC MASS UNITamu is an arbitrarily chosen amount.

It is so small, it is not practical for actual use..

A person named Avogardo, invented a multiple that would allow the MASS RATIO to be preserved but to be measured in grams.

He called it : a mole

P310-3178The MoleA mole of any element is defined to be

the same number of atoms of that element equal to the number of atoms in 12.0 g of carbon-12

P310-3179The mass of 1 mole (in grams)Equal to the numerical value of the average atomic mass (get from periodic table) 1 mole of C atoms= 12.01 g1 mole of Mg atoms =24.31 g1 mole of Cu atoms =63.55 gWhere are these numbers from?PERIODIC TABLE

Molar Mass10Other Names Related to Molar MassAtomic MassSingle atom, mass is measured in amus instead of grams. Only the units are different:Atomic/Individual/MICROSCOPIC = amu Molar/A lot of/VISIBLE/MACROSCOPIC = g11Find the molar mass (usually we round to the hundreds place)Learning Check!1 mole of Br atoms

1 mole of Sn atoms=79.90 g/mole= 118.71 g/moleMass in grams of 1 mole equal numerically to the sum of the atomic masses1 mole of CaCl2 = 110.98 g/mol (1 mole Ca x 40.08 g/mol ) + (2 moles Cl x 35.45 g/mol) = 110.98 g/mol CaCl2

Molar Mass of Molecules and CompoundsMass in grams of 1 mole equal numerically to the sum of the atomic masses1 mole of N2O4 Molar Mass of Molecules and Compounds= 92.02 g/molMolar Mass of K2O =

B. Molar Mass of antacid Al(OH)3 = K2O = 94.20 g/molAl(OH)3 = 78.03 g/mol

Learning Check!Other Names Related to Molar MassMolecular Mass/Molecular Weight: Single molecule, mass is measured in amus instead of grams. same numerical value as 1 mole of molecules. Only the units are different:Individual/MICROSCOPIC= amuA lot of/VISIBLE/MACROSCOPIC= g16Other Names Related to Molar MassMolecular Mass/Molecular Weight: Single molecule, mass is measured in amus instead of grams. But, the molecular mass/weight is the same numerical value as 1 mole of molecules. Only the units are differentFormula Mass/Formula Weight: Same goes for compounds. But again, the numerical value is the same. Only the units are different.Other Names Related to Molar MassTHE POINT: You may hear all of these terms which mean the SAME NUMBER just different unitsMolar Mass = Gram Formula Weight in our textbook

With Avogadros #, you may also hear the terms: molecules, atoms, formula units, ions, particles, thingsIT DEPENDS ON WHAT YOURE TALKING ABOUT:example: 1 dozen eggs versus 1 dozen roses1 mole of H2O molecules vs. 1 mole of NaCl formula unitsProzac, C17H18F3NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass.

309.38 gramsLearning Check

molar mass Grams Moles

Calculations with Molar MassDo you multiply or divide by molar mass?It depends on which way youre going.Use conversion factors. Aluminum is often used for the structure of light-weight bicycle frames. How many grams of Al are in 3.00 moles of Al?3.00 moles Al ? g Al

Converting Moles and GramsMolar mass of 1 mole Al = 26.98 g Al

2. Conversion factors for Al 26.98 g Al or 1 mol Al 1 mol Al 26.98g Al

3. Setup3.00 moles Al x 26.98 g Al =1 mole AlAnswer = 81.0 g Al Iron (III) oxide is often called rust, it forms when iron metal reacts with moisture. How many moles of Fe2O3 are in 3.00 grams of Fe2O3?3.00 grams of Fe2O3? moles Fe2O3 Converting Moles and Grams

1. Molar mass of Fe2O3 YOU MUST CALCULATE IT!2. Conversion factors for Fe2O3 ? g Fe2O3 or 1 mol Fe2O3 1 mol Fe2O3 ? g Fe2O3

3. Setup3.00 grams Fe2O3 x 1 moleFe2O3 ? grams Fe2O3

Answer = 0.0188 mol Fe2O3 1. Molar mass of Fe2O3 159.70 grams2. Conversion factors for Fe2O3 159.70 g Fe2O3 or 1 mol Fe2O3 1 mol Fe2O3 159.70 g Fe2O3

3. Setup3.00 grams Fe2O3 x 1 moleFe2O3 159.70 g Fe2O3Answer = 0.0 188 mole Fe2O3 The artificial sweetener aspartame (Nutra-Sweet) formula C14H18N2O5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame?

Learning Check!

225 g C14H18N2O5 = ? mol C14H18N2O5

225g x _?__mol__ = mol ? g

Setting it up:Do you know a relationship between moles and grams for C14H18N2O5 ? 225 g C14H18N2O5 = ? mol C14H18N2O5

The relationship is: MOLAR MASS!

1 mol = the sum of the atomic masses from the periodic table in grams!

225g x _1__mol__ = ? mol ? g

Setting it up: 225 g C14H18N2O5 = ? mol C14H18N2O5

225g x _1__mol__ = ? mol 294.34 gHow do you enter this in your calculator?

Setting it up:Enter first number first, multiply numerators, divide by denominators.225 x 1 / 294.35 =