Molar Relationships

Dozen = 12 Names associated with an amount Pair = 2 Can you think of any more?????

The Mole….. The mole (mol) is the amount of a substance that contains as many elementary entities as there are atoms in exactly 12.00 grams of 12C 1 mol = NA = 6.0221367 x 1023 Avogadro’s number (NA)

What is the mass of one mole of: C Hg Cu Fe 3.2

Molar Mass The 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 = 1 mole of Cu atoms = 1 mole of S atoms = 1mole of Hg atoms = 1 mole of Fe atoms =

Learning Check! = 79.9 g/mole 1 mole of Br atoms 1 mole of Sn atoms Find the molar mass (usually we round to the tenths place) = 79.9 g/mole 1 mole of Br atoms 1 mole of Sn atoms = 118.7 g/mole

molecular mass (amu) = molar mass (grams) Molecular mass (or molecular weight) is the sum of the atomic masses (in amu) in a molecule. SO2 1S 32.07 amu 2O + 2 x 16.00 amu SO2 64.07 amu For any molecule molecular mass (amu) = molar mass (grams) 1 molecule SO2 = 64.07 amu 1 mole SO2 = 64.07 g SO2 Let’s try some more…………….. 3.3

Molar Mass of Molecules and Compounds Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of CaCl2 = 111.1 g/mol 1 mole Ca x 40.1 g/mol + 2 moles Cl x 35.5 g/mol = 111.1 g/mol CaCl2 Practice with this one: 1 mole of N2O4 =

Learning Check! Molar Mass of K2O = ? Grams/mole B. Molar Mass of antacid Al(OH)3 = ? Grams/mole

Learning Check Prozac, C17H18F3NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass.

So, if one mole = the formula mass how do we calculate…. The mass of 05 mol of Calcium Carbonate The mass of 2.25 mol of Sodium Chloride

How many moles are there in? 100 g of Magnesium Hydroxide ? 64 g of Oxygen ?

Converting to # of atoms or molecules How many atoms are in 3.00 moles of Iron? How many atoms are in 0.25 moles of Water?

Molar Mass The molar mass of a compound is found by adding Together the molar masses of all of its elements, taking Into account the number of moles of each element present. Homework: pg 157 # 5-11

Factor-Label Method (also called… dimensional analysis) Use fractions that include numbers and units to convert from one item to another. All fractions must have a valued of “1” Example problem: How many seconds are there in one year?

Types of Mole Conversion Problems: Grams to Moles --- Moles to Grams Example Problem: How many Moles are in 58 g of NaHCO3? How many grams are in 3.75 Moles of Water?

Moles Particles (atoms,ions,molecules) How many atoms are in .75 moles of Oxygen Gas? How many moles are in 2.709 x 1025 molecules of Calcium Hydroxide? How many hydroxide ions are there in 4.5 Moles of Calcium Hydroxide?

So… Percent Composition the percentage by mass of each element in a compound Percent = _______ Part Whole x 100% So… Percent composition of a compound or = molecule Mass of element in 1 mol ____________________ x 100% Mass of 1 mol

Percent Composition Molar Mass of KMnO4 K = 1(39.1) = 39.1 Example: What is the percent composition of Potassium Permanganate (KMnO4)? Molar Mass of KMnO4 K = 1(39.1) = 39.1 Mn = 1(54.9) = 54.9 O = 4(16.0) = 64.0 MM = 158 g

Percent Composition Molar Mass of KMnO4 = 158 g 39.1 g K % K x 100 = Example: What is the percent composition of Potassium Permanganate (KMnO4)? Molar Mass of KMnO4 = 158 g 39.1 g K % K x 100 = 24.7 % 158 g 54.9 g Mn 34.8 % x 100 = % Mn 158 g K = 1(39.10) = 39.1 64.0 g O x 100 = 40.5 % Mn = 1(54.94) = 54.9 % O 158 g O = 4(16.00) = 64.0 MM = 158

Percent Composition Determine the percentage composition of sodium carbonate (Na2CO3)? Molar Mass Percent Composition 46.0 g x 100% = 43.4 % Na = 2(23.00) = 46.0 C = 1(12.01) = 12.0 O = 3(16.00) = 48.0 MM= 106 g % Na = 106 g 12.0 g x 100% = 11.3 % % C = 106 g 48.0 g x 100% = 45.3 % % O = 106 g

Hydrates Hydrated salt – salt that has water molecules trapped within the crystal lattice Examples: CuSO4•5H2O , CuCl2•2H2O Anhydrous salt – salt without water molecules Examples: CuCl2 Can calculate the percentage of water in a hydrated salt.

Hydrated Compounds: Chemicals that usually have water associated with them. How they are written: BaCl2. 2H2O – Barium Chloride dihydrate CuSO4.5H2O – Copper Sulfate pentahydrate NaCO3.10H2O-__________________

Percent Composition If 145 grams of copper (II) sulfate pentahydrate is completely dehydrated, how many grams of anhydrous copper sulfate will remain? CuSO4 . 5 H2O 1. Molar Mass 2. % CuSO4 Cu = 1 x 63.55 = 63.55 g S = 1 x 32.06 = 32.06 g O = 4 x 16.00 = 64.00 g MM = 159.61 g 159.6 g X 100 = 63.92 % 249.7 g 3. Grams anhydrous CuSO4 H = 2 x 1.01 = 2.02 g O = 1 x 16.00 = 16.00 g MM = 18.02 g 0.6392 x 145 = 92.7 g Mass of 5 moles of H2O = 5 x 18.02 g = 90.1 g Total Molar mass = 159.6 g + 90.1 g = 249.7 g

Calculate the Molar Mass of Hydrates-- ZnSO4.7H2O Na2CO3.10H2O

Formulas Percent composition allow you to calculate the simplest ratio among the atoms found in compound. Empirical Formula – formula of a compound that expresses lowest whole number ratio of atoms. Molecular Formula – actual formula of a compound showing the number of atoms present Examples: C6H12O6 - molecular C4H10 - molecular C2H5 - empirical CH2O - empirical

Determining Empirical Formula PERCENT Grams in 100g sample Moles Mole Ratio Empirical Formula C 40 % 40 g H 6.71% 6.71 g O 53.3% 53.3 g

Try this one: An oxide of aluminum is formed by the reaction of 4 Try this one: An oxide of aluminum is formed by the reaction of 4.151 g of aluminum with 3.692g of oxygen. Calculate the empirical formula. E L ments PERCENT Grams in 100g sample Moles Mole Ratio Empirical Formula

A 4. 550 g sample of cobalt reacts with 5 A 4.550 g sample of cobalt reacts with 5.475 g chlorine to form a binary compound. Determine the empirical formula for this compound. E L ments PERCENT Grams in 100g sample Moles Mole Ratio Empirical Formula