Unit 17: Review All the Things. Part I

LPChem1415 Groups of similar elements have special names:

LPChem1415 # valence electrons increases, left to right:

Valence Electrons & Stability Main Group Ion Charges LPChem ±4± Positive charge means electrons were REMOVED. Negative charge means electrons were ADDED.

Ionic Nomenclature: Roman Numerals  Fe 2 (CO 3 ) 3 = iron ( ? ) carbonate LPChem1415 Fe 2 (CO 3 ) ( ) 3 = 06+ ( ) Iron (III) carbonate

C. Molar Conversions molar mass (formula mass) (g/mol) MASS IN GRAMS MOLES NUMBER OF PARTICLES Avogadro 6.02  (particles/mol)

C. Molar Conversions molar mass (formula mass) mass (grams) FM MASS IN GRAMS MOLES NUMBER OF PARTICLES Avogadro 6.02  Particles Avogadro = moles=

A. Molarity n 1. Concentration of a solution. total combined volume substance being dissolved

B. Molality n 1. Concentration of a solution. Mass of solvent substance being dissolved

What is the percent composition of Cu 2 S? Copper: 2(63.55) / = Cu 2 S has a molar mass of: A. Percentage Composition 2(63.55) = = % Cu Sulfur: 1(32.06) / = = % S

C. Johannesson B. Empirical Formula C2H6C2H6 CH 3 reduce subscripts n Smallest whole number ratio of atoms in a compound

C. Johannesson B. Empirical Formula 1. Find mass (or %) of each element. 2. Find moles of each element. 3. Divide moles by the smallest # to find subscripts. 4. When necessary, multiply subscripts by 2, 3, or 4 to get whole #’s.

C. Johannesson B. Empirical Formula n Find the empirical formula for a sample of 25.9% N and 74.1% O g 1 mol g = 1.85 mol N 74.1 g 1 mol g = 4.63 mol O 1.85 mol = 1 N = 2.5 O

C. Johannesson B. Empirical Formula N 1 O 2.5 Need to make the subscripts whole numbers  multiply by 2 N2O5N2O5

C. Johannesson C. Molecular Formula n “True Formula” - the actual number of atoms in a compound CH 3 C2H6C2H6 empirical formula molecular formula ?

C. Johannesson C. Molecular Formula 1. Find the empirical formula. 2. Find the empirical formula mass. 3. Divide the molecular mass by the empirical mass. 4. Multiply each subscript by the answer from step 3.

C. Molecular Formula n The empirical formula for ethylene is CH 2. Find the molecular formula if the molecular mass is 28.1 g/mol? 28.1 g/mol g/mol = 2.00 empirical mass = g/mol (CH 2 ) 2  C 2 H 4

C. Johannesson A.Signs of a Chemical Reaction n Evolution of heat and light n Formation of a gas n Formation of a precipitate n Color change

C. Johannesson B.Law of Conservation of Mass n mass is neither created nor destroyed in a chemical reaction 4 H 2 O 4 H 2 O 4 g32 g 36 g n total mass stays the same n atoms can only rearrange

C. Johannesson C. Chemical Equations A+B  C+D REACTANTSPRODUCTS

C. Johannesson Al + CuCl 2  Cu + AlCl 3 Al Cu Cl  3  6   C. Balancing Example Aluminum and copper(II) chloride react to form copper and aluminum chloride. 2  2  6

D. Stoichiometry Problems  How many moles of KClO 3 must decompose in order to produce 9 moles of oxygen gas? 9 mol O 2 2 mol KClO 3 3 mol O 2 = 6 mol KClO 3 2KClO 3  2KCl + 3O 2 ? mol9 mol

D. Stoichiometry Problems  How many grams of silver will be formed from 12.0 g copper? 12.0 g Cu 1 mol Cu g Cu = 40.7 g Ag Cu + 2AgNO 3  2Ag + Cu(NO 3 ) 2 2 mol Ag 1 mol Cu g Ag 1 mol Ag 12.0 g? g