Hi Guys & Gals! Warm-Up Time!

Hi Guys & Gals! Warm-Up Time! Draw the Lewis Structure and give the molecular shape and molecular polarity of the following molecules: • H2S • CHCl3 • SO3 • O2 Lower case L

Hi Guys & Gals! Quiz Time! Give the name or formula of the following provided the opposite. H3PO4 CF4 NaNO3 C2H4 SO2 Methane Nitrogen trihydride Ammonium hydroxide Ethanol Hydrochloric acid

Follow along in your textChapter 7 Sections 1 & 2Pages 224 - 240 The Mole

VERY A large amount!!!! What is the Mole? • A counting number (like a dozen) • Avogadro’s number (NA) • 1 mol = 6.02  1023 particles

HOW LARGE IS IT??? • 1 mole of pennies would cover the Earth 1/4 mile deep! • 1 mole of hockey pucks would equal the mass of the moon! • 1 mole of basketballs would fill a bag the size of the earth!

Molar Mass • Mass of 1 mole of an element or compound. • Atomic mass tells the... • atomic mass units per atom (amu) • grams per mole (g/mol) • Usually rounded to 2 decimal places

Molar Mass Examples 12.01 g/mol 26.98 g/mol 65.39 g/mol • 1 mol of carbon • 1 mole of aluminum • 1 mole of zinc

Molar Mass Examples • water • sodium chloride • H2O • 2(1.01) + 16.00 = 18.02 g/mol • NaCl • 22.99 + 35.45 = 58.44 g/mol

Molar Mass Examples • sodium bicarbonate • sucrose • NaHCO3 • 22.99 + 1.01 + 12.01 + 3(16.00) = 84.01 g/mol • C12H22O11 • 12(12.01) + 22(1.01) + 11(16.00) = 342.34 g/mol

Relative Atomic Mass& Percentage Composition Follow along in your text Chapter 7 Sections 2 & 3 Pages 234 - 248

Relative Atomic Mass • Is the same as Average Atomic Mass • The percent of each isotope of an element is used to find the average mass of that element. (mass A1 x % of A1) + (mass A2 x % of A2) 100 = Average Mass of A This was done earlier in the year. Remember the Skittlesium Lab?

Relative Atomic Mass • Calculate the average atomic mass of rubidium if 72.17% of its atoms have a mass of 84.91 amu and 27.83% of its atoms have a mass of 86.91 amu (84.91 x 72.17%) + (86.91 x 27.83%) = 85.47 amu

Percentage Composition • the percentage by mass of each element in a compound

127.10 g Cu 159.17 g Cu2S 32.07 g S 159.17 g Cu2S Percentage Composition • Find the % composition of Cu2S.  100 = %Cu = 79.852% Cu %S =  100 = 20.15% S

28 g 36 g 8.0 g 36 g Percentage Composition • Find the percentage composition of a sample that is 28 g Fe and 8.0 g O.  100 = 78% Fe %Fe =  100 = 22% O %O =

Percentage Composition • How many grams of copper are in a 38.0-gram sample of Cu2S? Cu2S is 79.852% Cu (38.0 g Cu2S)(0.79852) = 30.3 g Cu

36.04 g 147.02 g Percentage Composition • Find the mass percentage of water in calcium chloride dihydrate, CaCl2•2H2O? 24.51% H2O %H2O =  100 =

Empirical Formula& Molecular Formula Follow along in your text Chapter 7 Sections 3 Pages 234 - 248

CH3 Empirical Formula • Smallest whole number ratio of atoms in a compound C2H6 reduce subscripts

Empirical Formula 1. Find mass of each element. If given percent, just say it’s a mass. 2. Find moles of each element. 3. Divide all moles by the smallest mole to find subscripts. 4. When necessary, multiply subscripts to get whole #’s. If number ends in…multiply by… ≈ 0.50 2 ≈ 0.33 3 ≈ 0.25 4

1.85 mol 1.85 mol Empirical Formula • Find the empirical formula for a sample of 25.9% N and 74.1% O. 25.9 g 1 mol 14.01 g = 1.85 mol N = 1 N 74.1 g 1 mol 16.00 g = 4.63 mol O = 2.5 O

N2O5 Empirical Formula N1O2.5 Need to make the subscripts whole numbers  multiply by 2

C2H6 Molecular Formula • “True Formula” - the actual number of atoms in a compound CH3 empirical formula ? molecular formula

Molecular Formula 1. Find the empirical formula (EF). 2. Find the empirical formula mass. 3. Divide the molecular formula (MF) mass by the empirical mass. 4. Multiply each subscript of the empirical formula by the answer from step 3.

28.1 g/mol 14.03 g/mol Molecular Formula • The empirical formula for ethylene is CH2. Find the molecular formula if the molecular mass is 28.1 g/mol? empirical formula mass = 14.03 g/mol = 2.00 (CH2)2  C2H4

Hi Guys & Gals! Warm-Up Time!