Warm-up Give the names for the following: CS2, CrO, CH4 and MgCl2 Give the formulas for the following: Nitric acid, aluminum oxide, copper (III) oxide, and dinitrogen pentoxide What are the numbers on top and below an element on the periodic table? Give a definition for the number below an element?

Holey Moley!

Ewwww….Moles!

Moles…in Chemistry?

1 mole = 6.022 X 1023 particles (atoms/molecules)

1 mol of 6.022 X 1023 atoms of Mg 1 mol of 6.022 X 1023 atoms of C 1 mol of 6.022 X 1023 atoms of V

1 mol of 6.022 X 1023 molecules of H2O 1 mol of 6.022 X 1023 molecules of CH4 4

g/mol g/mol Molar Mass g/mol

1 mol of 12.011 g of Carbon 1 mol of 1.0078 g of Hydrogen

Conversion Factors 1 mole of substance = 6.022 X 1023 atoms/molecules 1 mole of substance = molar mass Molar mass = 6.022 X 1023 atoms/molecules

12 grams of K2S molecules

On Your Own! 1000 grams of calcium is ______ moles of calcium What is the mass of 3 moles of carbon disulfide? How many moles of ammonia, NH3, are in 51 grams of NH3 A chemist needs 3 moles of aluminum oxide for an experiment. How many grams of aluminum oxide should she weigh out? How many molecules of nitric acid are in 5 grams of nitric acid? You guess that a solution of CrO contains 5.0 X 1020 molecules. How many moles of CrO would be in this solution?

Warm-up Give the name or the formula for the following: K2CO3 Nitric Acid Hydrochloric Acid Cu(OH)3 C5H10 1.801 X 1024 atoms Cu = ? g Cu What is the molar mass for C11H12O11? Define (in your words) the term “composition.”

Chemistry’s Cornucopia

Cornucopia Definition: an abundant supply of good things that are different.

Percent Composition The percent by mass of each element present in a compound. % composition = 𝑇𝑜𝑡𝑎𝑙 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑙𝑒𝑚𝑒𝑛𝑡 𝑇𝑜𝑡𝑎𝑙 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑 𝑋 100 Mass is determined using the molar mass of an element.

Mn(CHO2)2 Mn H O O C C H O O

On Your Own! Find the percent composition for each element of the following compounds: C12H22O11 Sulfuric Acid Potassium Permanganate Chromium (III) Sulfide Acetic Acid

𝐶𝑜 𝐶𝑙 2 ∙6 𝐻 2 𝑂 Hydrates Cobalt (II) Chloride is hydrated A compound in which water molecules are chemically bound. Typically inorganic salts. In other words, it absorbs water! Cannot leave hydrates open to air. 𝐶𝑜 𝐶𝑙 2 ∙6 𝐻 2 𝑂 Cobalt (II) Chloride is hydrated by 6 molecules of water

Percent Composition of Hydrates We use percent composition to determine the percent of water in a hydrate. Important in determining unknown hydrates. What is the percent water in Cobalt (II) Chloride Hexahydrate? https://www.youtube.com/watch?v=OuF4hjTFdsg

On Your Own! Determine the percent water for the following hydrates: 1. 𝐶𝑜 𝐶𝑙 2 ∙6 𝐻 2 𝑂 2. 𝑁𝑎 2 𝐶𝑂 3 ∙10 𝐻 2 𝑂 3.𝑀𝑔 𝑆𝑂 4 ∙7 𝐻 2 𝑂 4.𝐶𝑢 𝑆𝑂 4 ∙5 𝐻 2 𝑂

Calculating Empirical and Molecular Formulas “Step by Step” Calculating Empirical and Molecular Formulas

CH2 1C:2H Empirical Formula “There is 1 carbon for every 2 hydrogens” The simplest formula of a compound. The smallest ratio of elements in a compound. Represents the composition of elements in a compound. CH2 1C:2H “There is 1 carbon for every 2 hydrogens”

C4H8 4C:8H Molecular Formula A multiple of the empirical formula. The actual ratio of elements in a compound. Represents the structure of elements in a compound. C4H8 4C:8H “There are 4 carbons for every 8 hydrogens”

Represents composition Empirical The simplest formula Smallest ratio Represents composition CH2 1:2 ratio Molecular A multiple Actual ratio Represents structure C4H8

Empirical Formula Practice

“Step by Step” Change percentage to grams assuming there are 100g of the sample Divide by the molar mass of each element Divide the moles of each element by the lowest number of moles of all the elements Round to whole numbers to find ratios UNLESS there is .5, then multiply each result by 2 for whole number ratios Write the formula!

Problem 1 The percent composition of a compound was found to be 63.5% Silver, 8.2% Nitrogen, and 28.3% oxygen. Determine the compound’s empirical formula.

Problem 2 A 170.00g sample of an unidentified compound contains 29.84g of Sodium, 67.49g Chromium, and 72.67g Oxygen. What is the compounds empirical formula?

Problem 3 A 60.00g sample of an tetraethyl lead, a gasoline additive, contains 38.43g of Lead, 17.83g Carbon, and 3.74g Hydrogen. What is the compounds empirical formula?

Warm-up Calculate the following conversions: 88g AgNO3 → molecules of AgNO3 5 mL of HF → molecules of HF (density = 1.15 g/mL) What is the percent composition of H2SO4? A 60.00g sample of an tetraethyl lead, a gasoline additive, contains 38.43g of Lead, 17.83g Carbon, and 3.74g Hydrogen. What is the compounds empirical formula?

Molecular Formula Practice

“Step by Step” Calculate empirical formula Calculate the mass of the empirical formula Divide the given mass by the empirical mass, this will give you an element multiplier Multiply your chemical quantities by the multiplier Rewrite molecular formula with new chemical values

Problem 1 A compound contains 7.19% phosphorus and 92.81% bromine. If this compound has a molecular mass of 431g/mol, what is the molecular formula?

Problem 2 Naphthalene is a carbon and hydrogen containing compound often used in moth balls. The empirical formula is C5H4 and its molar mass is 128.16g/mol. Find the molecular formula.

Investigating Chemical Reactions Evidence of Chemical Reactions

Prime Suspects 𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠→𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠 Prime Suspects: Atom and Molecule Group Affiliation: Chemical Reactions Group Symbol: 𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠→𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠 Crime: Breaking and forming bonds

Evidence #1 Precipitate Formation Highly predictable crime if we analyze solubility rules. Soluble = dissolves in solution Insoluble = forms a precipitate (solid) Surveillance Footage: https://www.youtube.com/watch?v=Qc2pWUIzP2k

Evidence #2 Color Change Intensity of color a result of a reactants being dilute or concentrated. Surveillance Footage https://www.youtube.com/watch?v=OKurcQt3ZOU

Evidence # 3 Temperature change Endothermic - Absorbs heat (+∆𝐻), temperature decreases Exothermic - Releases heat (-∆𝐻), temperature increases Surveillance Footage: https://www.youtube.com/watch?v=BTDRtSGNMtM

Common Tests for Chemical Reactions Burning Splint – tests for oxygen, hydrogen, or carbon dioxide https://www.youtube.com/watch?v=LiAvDpl5aJA Lime water – tests for carbon dioxide https://www.youtube.com/watch?v=QR6GsydYUSI

Warm-up A compound contains 7.19% phosphorus and 92.81% bromine. If this compound has a molecular mass of 431g/mol, what is the molecular formula? Convert the following: 1.8 x 1024 atoms Br → g Br What are the three evidences for chemical reactions? Is ice melting endothermic or exothermic?

Types of Reactions

Synthesis

Decomposition

Single Replacement

Double Replacement

Combustion

Identifying Reactions Identify the following reactions:

Balancing Chemical Reactions Finding Your Balance Balancing Chemical Reactions

Balancing…What does it all mean?

Balancing Chemical Reactions Simple: elements on the reactant side must equal the elements on the product side. Law of Conservation of Mass 𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠→𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠 products reactants

The Law of the Conservation of Mass