General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake 6.1 Equations for Chemical Reactions Chapter 6 Chemical Reactions and Quantities © 2013 Pearson Education, Inc. Lectures

© 2013 Pearson Education, Inc. Chapter 6, Section 1 2 Chemical Change A chemical change occurs when a substance is converted into one or more new substances. Chemical changes can be recognized by  a change in color,  the formation of a solid, or  the formation of bubbles. A chemical change produces new substances. When silver (Ag) reacts with sulfur (S), it produces silver sulfide (Ag 2 S).

© 2013 Pearson Education, Inc. Chapter 6, Section 1 3 Evidence of Chemical Change

© 2013 Pearson Education, Inc. Chapter 6, Section 1 4 Chemical Reactions A chemical reaction  involves the rearrangement of atoms.  produces one or more new substances.  can be observed by the appearance of new physical properties. A chemical reaction forms new products with different properties. An antacid (NaHCO 3 ) tablet in water forms bubbles of carbon dioxide (CO 2 ).

© 2013 Pearson Education, Inc. Chapter 6, Section 1 5 Writing a Chemical Equation A chemical equation tells us what substances react (reactants) and what substances are formed (products).

© 2013 Pearson Education, Inc. Chapter 6, Section 1 6 Writing a Chemical Equation Reaction Description: In a Bunsen burner, natural gas (methane, CH 4 ) burns in oxygen, producing carbon dioxide gas and water vapor. Skeleton Equation: Identify the reactants (CH 4 and O 2 ) and products (CO 2 and H 2 O) and write equation: CH 4(g) + O 2(g)  CO 2(g) + H 2 O (g)

© 2013 Pearson Education, Inc. Chapter 6, Section 1 7 Equation for a Chemical Reaction

© 2013 Pearson Education, Inc. Chapter 6, Section 1 8 Law of Conservation of Mass Fundamental scientific law, first established in the late 1790’s by French chemist Antoine LaVoisier  known as the father of modern chemistry LaVoisier showed that the total mass of the reactants in a chemical reaction always equals the total mass of the products “For any chemical reaction, the mass of the reactants always equals the mass of the products” 8

© 2013 Pearson Education, Inc. Chapter 6, Section 1 9 Balanced Chemical Equations In a balanced chemical equation, the number of atoms in the reactants is equal to the number of atoms in the products for each element.

© 2013 Pearson Education, Inc. Chapter 6, Section 1 10 Balancing Chemical Equations To balance a chemical equation,  whole number coefficients are placed in front of the chemical formulas.  coefficients in front of a molecule represent the multiple of that molecule needed in a balanced reaction.  subscripts are never changed.

© 2013 Pearson Education, Inc. Chapter 6, Section 1 11 Checking a Balanced Equation Atoms C11 Atoms H44 Atoms O44 Reactants Products balanced

© 2013 Pearson Education, Inc. Chapter 6, Section 1 12 Guide to Balancing a Chemical Equation

© 2013 Pearson Education, Inc. Chapter 6, Section 1 13 Steps to Balancing a Chemical Equation Balance the following chemical reaction: Ethanol (C 2 H 6 O) burns in the presence of oxygen gas(O 2 ) to produce steam (H 2 O) and carbon dioxide (CO 2 ) gas. Step 1 Write an equation using the correct formulas of the reactants and products.

© 2013 Pearson Education, Inc. Chapter 6, Section 1 14 Steps to Balancing a Chemical Equation Step 2 Count the atoms of each element in the reactants and products. Reactants Products not balanced balanced Atoms of C21 Atoms of H62 Atoms of O33

© 2013 Pearson Education, Inc. Chapter 6, Section 1 15 Steps to Balancing a Chemical Equation Step 3 Use coefficients to balance each element. Step 4 Check the final equation to confirm it is balanced. Create a balance sheet to count atoms of each element. Reactants Products balanced Atoms of C22 Atoms of H66 Atoms of O77

© 2013 Pearson Education, Inc. Chapter 6, Section 1 16 Learning Check Determine if each equation is balanced or not.

© 2013 Pearson Education, Inc. Chapter 6, Section 1 17 Write a balanced equation for the reaction of nitrogen gas (N 2 ) with hydrogen gas (H 2 ) to form ammonia gas (NH 3 ). Learning Check

© 2013 Pearson Education, Inc. Chapter 6, Section 1 18 Check the balance of atoms in the following equation: 1. number of H atoms in products A. 2B. 4C number of O atoms in reactants A. 2B. 4C number of Fe atoms in reactants A. 1B. 3C. 4 Learning Check

© 2013 Pearson Education, Inc. Chapter 6, Section 1 19 Equations with Polyatomic Ions When balancing equations with polyatomic ions that remain the same on both sides of the equation, balance them as a unit.

© 2013 Pearson Education, Inc. Chapter 6, Section 1 20 Balancing with Polyatomic Ions Balance the following chemical equation. Step 1 Write the equation using the correct formulas of the reactants and products.

© 2013 Pearson Education, Inc. Chapter 6, Section 1 21 Balancing with Polyatomic Ions Balance the following chemical equation. Step 2 Count the atoms of each element in the reactants and products. Reactants Products not balanced Atoms of Na31 PO 4 3− ions12 Atoms of Mg13 Atoms of Cl21

© 2013 Pearson Education, Inc. Chapter 6, Section 1 22 Balancing with Polyatomic Ions Step 3 Use coefficients to balance each element. Step 4 Check the final equation to confirm it is balanced. Atoms of Na66 PO 4 3− ions22 Atoms of Mg33 Atoms of Cl66 Balance the following chemical equation. ReactantsProducts balanced

© 2013 Pearson Education, Inc. Chapter 6, Section 1 23 Balance and list the coefficients from reactants to products. 1. __Fe 2 O 3 (s) + __C(s) __Fe(s) + __CO 2 (g) A. 2, 3, 2,3 B. 2, 3, 4, 3 C. 1, 1, 2, 3 2. __Al(s) + __FeO(s) __Fe(s) + __Al 2 O 3 (s) A. 2, 3, 3, 1 B. 2, 1, 1, 1 C. 3, 3, 3, 1 3. __Al(s) + __H 2 SO 4 (aq) __Al 2 (SO 4 ) 3 (aq) + __H 2 (g) A. 3, 2, 1, 2 B. 2, 3, 1, 3 C. 2, 3, 2, 3 Learning Check

General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake 6.2 Types of Reactions Chapter 6 Chemical Reactions and Quantities © 2013 Pearson Education, Inc. Lectures

© 2013 Pearson Education, Inc. Chapter 6, Section 2 25 Types of Reactions Chemical reactions can be classified as  combination reactions,  decomposition reactions,  single replacement reactions,  double replacement reactions, or  combustion reactions.

© 2013 Pearson Education, Inc. Chapter 6, Section 2 26 Combination Reaction In a combination reaction, two or more elements (or simple compounds) combine to form one product.

© 2013 Pearson Education, Inc. Chapter 6, Section 2 27 Formation of MgO

© 2013 Pearson Education, Inc. Chapter 6, Section 2 28 Decomposition Reaction In a decomposition reaction, one substance splits into two or more simpler substances.

© 2013 Pearson Education, Inc. Chapter 6, Section 2 29 Decomposition of HgO

© 2013 Pearson Education, Inc. Chapter 6, Section 2 30 Single Replacement Reaction In a single replacement reaction, one element takes the place of a different element in a reacting compound.

© 2013 Pearson Education, Inc. Chapter 6, Section 2 31 Zn and HCl Combine in a Single Replacement Reaction

© 2013 Pearson Education, Inc. Chapter 6, Section 2 32 Double Replacement Reaction In a double replacement reaction, the two positive ions in the reacting compounds exchange places.

© 2013 Pearson Education, Inc. Chapter 6, Section 2 33 Example of Double Replacement

© 2013 Pearson Education, Inc. Chapter 6, Section 2 34 Combustion Reaction In a combustion reaction, a carbon-containing compound that is the fuel burns in oxygen from the air to produce carbon dioxide (CO 2 ), water (H 2 O), and energy in the form of heat or a flame.

© 2013 Pearson Education, Inc. Chapter 6, Section 2 35 Combustion Reaction

© 2013 Pearson Education, Inc. Chapter 6, Section 2 36 Summary Reaction Types

© 2013 Pearson Education, Inc. Chapter 6, Section 2 37 Learning Check Classify the following reactions as a combination or decomposition reaction.

© 2013 Pearson Education, Inc. Chapter 6, Section 2 38 Learning Check Classify each of the following reactions as a single replacement or a double replacement reaction.

© 2013 Pearson Education, Inc. Chapter 6, Section 2 39 Learning Check Identify each of the following reactions as a combination, a decomposition, a single replacement, a double replacement, or a combustion reaction.

General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake 6.3 Oxidation–Reduction Reactions Chapter 6 Chemical Reactions and Quantities © 2013 Pearson Education, Inc. Lectures

© 2013 Pearson Education, Inc. Chapter 6, Section 3 41 Everyday Oxidation–Reduction Reactions In an oxidation–reduction reaction,  electrons are transferred from one substance to another.  if one substance loses electrons, another substance must gain electrons.  energy is provided to us from food.  electrical energy is provided in batteries.  iron rusts.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 42 In oxidation–reduction reactions,  the process of losing electrons is called oxidation. Oxidation Is a Loss of electrons. (OIL)  the process of gaining electrons is called reduction. Reduction Is a Gain of electrons. (RIG) Transfer of Electrons

© 2013 Pearson Education, Inc. Chapter 6, Section 3 43 Oxidation and Reduction

© 2013 Pearson Education, Inc. Chapter 6, Section 3 44 Oxidized or Reduced?

© 2013 Pearson Education, Inc. Chapter 6, Section 3 45 Oxidation and Reduction, Formation of CaS In the reaction:  the reactant, Ca has a charge of 0 and the product, CaS contains a Ca 2+ ion.  calcium loses two electrons, meaning oxidation has taken place.  the reactant, S has a charge of 0 and the product, CaS contains an S 2− ion.  sulfur gains two electrons, meaning reduction has taken place.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 46 Oxidation and Reduction, Formation of CaS Adding the two reactions, oxidation and reduction, gives us the overall reaction. The overall reaction is written as:

© 2013 Pearson Education, Inc. Chapter 6, Section 3 47 Zn and Cu 2+ When zinc is added to copper(II) sulfate, zinc undergoes oxidation, while copper undergoes reduction.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 48 Electron Transfer from Zn to Cu 2+ Oxidation: electron loss Reduction: electron gain

© 2013 Pearson Education, Inc. Chapter 6, Section 3 49 Identify each of the following reactions as oxidation or reduction. Learning Check

© 2013 Pearson Education, Inc. Chapter 6, Section 3 50 Learning Check In light-sensitive sunglasses, UV light initiates an oxidation-reduction reaction. 1. Which reactant is oxidized? 2. Which reactant is reduced?

© 2013 Pearson Education, Inc. Chapter 6, Section 3 51 Learning Check Identify the substances that are oxidized and reduced in each of the following reactions.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 52 Oxidation–Reduction in Biological Systems In biological systems, oxidation may involve  the loss of H or  the gain of O. In biological systems, reduction may involve  the gain of H or  the loss of O.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 53 Oxidation–Reduction in Biological Systems

© 2013 Pearson Education, Inc. Chapter 6, Section 3 54 Characteristics of Oxidation and Reduction

© 2013 Pearson Education, Inc. Chapter 6, Section 3 55 General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake 6.4 The Mole Chapter 6 Chemical Reactions and Quantities © 2013 Pearson Education, Inc. Lectures

© 2013 Pearson Education, Inc. Chapter 6, Section 3 56 Counting Units Counting terms are used to describe specific quantities.  1 dozen donuts = 12 donuts  1 ream of paper = 500 sheets  1 case = 24 cans

© 2013 Pearson Education, Inc. Chapter 6, Section 3 57 A mole is a counting unit that contains  the same number of particles as there are carbon atoms in 12.0 g of carbon 12 C.  6.02 x atoms of an element (Avogadro’s number). A Mole of Atoms

© 2013 Pearson Education, Inc. Chapter 6, Section mole of sulfur contains Avogadro’s number of atoms. A Mole of Sulfur

© 2013 Pearson Education, Inc. Chapter 6, Section 3 59 A mole  of a covalent compound has Avogadro’s number of molecules.  of an ionic compound contains Avogadro’s number of formula units. A Mole of a Compound

© 2013 Pearson Education, Inc. Chapter 6, Section 3 60 Number of Particles in One Mole

© 2013 Pearson Education, Inc. Chapter 6, Section 3 61 Avogadro’s number (6.02 x ) can be written as an equality and two conversion factors. Equality: Conversion Factors: Avogadro’s Number as an Equality

© 2013 Pearson Education, Inc. Chapter 6, Section 3 62 Guide to Calculating Atoms or Moles

© 2013 Pearson Education, Inc. Chapter 6, Section 3 63 Using Avogadro’s Number in Calculations How many Cu atoms are in 0.50 mole of Cu? Step 1 State the given and needed quantities. Analyze the Problem. Step 2 Write a plan to convert moles to atoms or molecules. moles of Cu Avogadro's number atoms of Cu GivenNeed 0.50 mole Cuatoms of Cu

© 2013 Pearson Education, Inc. Chapter 6, Section 3 64 Using Avogadro’s Number in Calculations How many Cu atoms are in 0.50 mole of Cu? Step 3 Use Avogadro’s number to write conversion factors.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 65 Using Avogadro’s Number in Calculations How many Cu atoms are in 0.50 mole of Cu? Step 4 Set up the problem to calculate the number of particles.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 66 Learning Check How many moles of CO 2 are in 2.50 x molecules of CO 2 ?

© 2013 Pearson Education, Inc. Chapter 6, Section 3 67 Subscripts State Atoms and Moles

© 2013 Pearson Education, Inc. Chapter 6, Section 3 68 Moles of Elements in a Formula The subscripts in a formula give  the relationship of atoms in the formula and  the moles of each element in 1 mole of a compound. Glucose C 6 H 12 O 6

© 2013 Pearson Education, Inc. Chapter 6, Section 3 69 Conversion Factors from Subscripts Subscripts used for conversion factors relate moles of each element in 1 mole of a compound For aspirin, C 9 H 8 O 4, can be written as:

© 2013 Pearson Education, Inc. Chapter 6, Section 3 70 Guide to Calculating Moles

© 2013 Pearson Education, Inc. Chapter 6, Section 3 71 Calculating Moles of an Element How many moles of carbon are present in 2.3 moles of C 5 H 10 O 2, propyl acetate, the compound that provides the odor and taste of pears. Step 1 State the given and needed quantities. Analyze the Problem. GivenNeed 2.3 moles of C 5 H 10 O 2 moles of C

© 2013 Pearson Education, Inc. Chapter 6, Section 3 72 Calculating Moles of an Element How many moles of carbon are present in 2.3 moles of C 5 H 10 O 2, propyl acetate, the compound that provides the odor and taste of pears. Step 2 Write a plan to convert moles of compound to moles of an element. moles of C 5 H 10 O 2 subscriptmoles of C

© 2013 Pearson Education, Inc. Chapter 6, Section 3 73 Calculating Moles of an Element How many moles of carbon are present in 2.3 moles of C 5 H 10 O 2, propyl acetate, the compound that provides the odor and taste of pears. Step 3 Write equalities and conversion factors using subscripts.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 74 Calculating Moles of an Element How many moles of carbon are present in 2.3 moles of C 5 H 10 O 2, propyl acetate, the compound that provides the odor and taste of pears. Step 4 Set up the problem to calculate the moles of an element.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 75 Learning Check How many O atoms are in mole of aspirin, C 9 H 8 O 4 ?

© 2013 Pearson Education, Inc. Chapter 6, Section 3 76 General, Organic, and Biological Chemistry Fourth Edition Karen Timberlake 6.5 Molar Mass Chapter 6 Chemical Reactions and Quantities © 2013 Pearson Education, Inc. Lectures

© 2013 Pearson Education, Inc. Chapter 6, Section 3 77 Molar mass is  the mass of one mole of a substance.  the number of grams that equals the atomic mass of that element. Molar Mass Molar mass is rounded to the tenths (0.1 g) place for use in this text.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 78 Give the molar mass of the following elements to the nearest 0.1 g. 1. K= ________ 2. Sn= ________ 3. Si= ________ Learning Check

© 2013 Pearson Education, Inc. Chapter 6, Section 3 79 Guide to Calculating Molar Mass

© 2013 Pearson Education, Inc. Chapter 6, Section 3 80 Molar Mass of CaCl 2 We calculate the molar mass of CaCl 2 to the nearest 0.1 g as follows. Analyze the Problem. Step 1 Obtain the molar mass of each element. GivenNeed formula unit CaCl 2 molar mass of Ca, Cl; CaCl 2

© 2013 Pearson Education, Inc. Chapter 6, Section 3 81 Molar Mass of CaCl 2 We calculate the molar mass of CaCl 2 to the nearest 0.1 g as follows. Step 2 Multiply each molar mass by the number of moles (subscript) in the formula. Grams from 1 mole of Ca Grams from 2 moles of Cl

© 2013 Pearson Education, Inc. Chapter 6, Section 3 82 Molar Mass of CaCl 2 We calculate the molar mass of CaCl 2 to the nearest 0.1 g as follows. Step 3 Calculate the molar mass by adding the masses of the elements.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 83 Learning Check Determine the molar mass of K 3 PO 4 to 0.1 g.

© 2013 Pearson Education, Inc. Chapter 6, Section 3 84 Prozac, C 17 H 18 F 3 NO, is an antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac? A g/mole B. 262 g/mole C. 309 g/mole Learning Check

© 2013 Pearson Education, Inc. Chapter 6, Section 3 85 One-Mole Quantities 32.1 g 55.9 g 58.5 g g g

© 2013 Pearson Education, Inc. Chapter 6, Section 3 86 Methane (CH 4 ), known as natural gas, is used in gas stoves and gas heaters. 1 mole of CH 4 = 16.0 g of CH 4 The molar mass of methane can be written as conversion factors Conversion Factors from Molar Mass

© 2013 Pearson Education, Inc. Chapter 6, Section 3 87 Calculations Using Molar Mass

© 2013 Pearson Education, Inc. Chapter 6, Section 3 88 How many moles are present in a 65.1 g sample of KCl? Step 1 State the given and needed quantities. Analyze the Problem. Step 2 Write a plan to convert grams to moles. grams of KCl Molar Mass moles of KCl Converting Mass to Moles, KCl GivenNeed 65.1 g of KClmoles of KCl

© 2013 Pearson Education, Inc. Chapter 6, Section 3 89 How many moles are present in a 65.1 g sample of KCl? Step 3 Determine the molar mass and write conversion factors. Step 4 Set up the problem to convert grams to moles. Converting Mass to Moles, KCl 1 mole of KCl = 74.6 g of KCl

© 2013 Pearson Education, Inc. Chapter 6, Section 3 90 Acetic acid, C 2 H 4 O 2, gives the sour taste to vinegar. Calculate the moles of acetic acid present in a 25.8 g sample. Learning Check

© 2013 Pearson Education, Inc. Chapter 6, Section 3 91 Connections between Mass, Moles, and Particles

© 2013 Pearson Education, Inc. Chapter 6, Section 3 92 Calcium carbonate, CaCO 3 is found in antacid tablets. If we have a mole sample of CaCO 3, how many grams are present? Learning Check