Chapter 5 Chemical Quantities and Reactions 5.1 The Mole Copyright © 2009 by Pearson Education, Inc.

Collection Terms A collection term states a specific number of items. 1 dozen donuts = 12 donuts 1 ream of paper = 500 sheets 1 case = 24 cans Copyright © 2009 by Pearson Education, Inc.

A Mole of Atoms A mole is a collection that contains the same number of particles as there are carbon atoms in 12.0 g of carbon. 6.02 x 1023 atoms of an element (Avogadro’s number). 1 mole element Number of Atoms 1 mole C = 6.02 x 1023 C atoms 1 mole Na = 6.02 x 1023 Na atoms 1 mole Au = 6.02 x 1023 Au atoms

A Mole of a Compound A mole of a covalent compound has Avogadro’s number of molecules. 1 mole CO2 = 6.02 x 1023 CO2 molecules 1 mole H2O = 6.02 x 1023 H2O molecules of an ionic compound contains Avogadro’s number of formula units. 1 mole NaCl = 6.02 x 1023 NaCl formula units 1 mole K2SO4 = 6.02 x 1023 K2SO4 formula units

Samples of 1 Mole Quantities 1 mole of C atoms = 6.02 x 1023 C atoms 1 mole of Al atoms = 6.02 x 1023 Al atoms 1 mole of S atoms = 6.02 x 1023 S atoms 1 mole of H2O molecules = 6.02 x 1023 H2O molecules 1 mole of CCl4 molecules = 6.02 x 1023 CCl4 molecules

Avogadro’s Number Avogadro’s number, 6.02 x 1023, can be written as an equality and two conversion factors. Equality: 1 mole = 6.02 x 1023 particles Conversion Factors: 6.02 x 1023 particles and 1 mole 1 mole 6.02 x 1023 particles

Using Avogadro’s Number Avogadro’s number is used to convert moles to particles convert particles to moles Copyright © 2009 by Pearson Education, Inc.

Converting Moles to Particles Avogadro’s number is used to convert moles of a substance to particles. How many Cu atoms are in 0.50 mole of Cu? 0.50 mole Cu x 6.02 x 1023 Cu atoms 1 mole Cu = 3.0 x 1023 Cu atoms Copyright © 2009 by Pearson Education, Inc.

Converting Particles to Moles Avogadro’s number is used to convert particles of a substance to moles. How many moles of CO2 are in 2.50 x 1024 molecules CO2? 2.50 x 1024 molecules CO2 x 1 mole CO2 6.02 x 1023 molecules CO2 = 4.15 moles of CO2

Learning Check 1. The number of atoms in 2.0 mole of Al atoms is A. 2.0 Al atoms. B. 3.0 x 1023 Al atoms. C. 1.2 x 1024 Al atoms. 2. The number of moles of S in 1.8 x 1024 atoms of S is A. 1.0 mole of S atoms. B. 3.0 moles of S atoms. C. 1.1 x 1048 moles of S atoms.

Subscripts and Moles The subscripts in a formula show the relationship of atoms in the formula. the moles of each element in 1 mole of compound. Glucose C6H12O6 In 1 molecule: 6 atoms C 12 atoms H 6 atoms O In 1 mole: 6 moles C 12 moles H 6 moles O

Subscripts State Atoms and Moles 9 moles of C 8 moles of H 4 moles of O

Factors from Subscripts The subscripts are used to write conversion factors for moles of each element in 1 mole of a compound. For aspirin, C9H8O4, the possible conversion factors are: 9 moles C 8 moles H 4 moles O 1 mole C9H8O4 1 mole C9H8O4 1 mole C9H8O4 and 1 mole C9H8O4 1 mole C9H8O4 1 mole C9H8O4 9 moles C 8 moles H 4 moles O

Learning Check A. How many moles of O are in 0.150 mole of aspirin, C9H8O4? B. How many atoms of O are in 0.150 mole of aspirin, C9H8O4?

Chapter 5 Chemical Quantities and Reactions 5.2 Molar Mass Copyright © 2009 by Pearson Education, Inc.

Molar Mass The molar mass is the mass of 1 mole of an element or compound. is the atomic or molecular mass expressed in grams. Copyright © 2009 by Pearson Education, Inc.

Molar Mass from Periodic Table is the atomic mass expressed in grams. 1 mole of Ag 1 mole of C 1 mole of S = 107.9 g = 12.01 g = 32.07 g Copyright © 2009 by Pearson Education, Inc.

Learning Check Give the molar mass for each (to the tenths decimal place). A. 1 mole of K atoms = ________ B. 1 mole of Sn atoms = ________

Molar Mass of a Compound The molar mass of a compound is the sum of the molar masses of the elements in the formula. Example: Calculate the molar mass of CaCl2. Element Number of Moles Atomic Mass Total Mass Ca 1 40.1 g/mole 40.1 g Cl 2 35.5 g/mole 71.0 g CaCl2 111.1 g

Molar Mass of K3PO4 Calculate the molar mass of K3PO4. Element Number of Moles Atomic Mass Total Mass in K3PO4 K P O

Some 1-mole Quantities 32.1 g 55.9 g 58.5 g 294.2 g 342.2 g One-Mole Quantities 32.1 g 55.9 g 58.5 g 294.2 g 342.2 g Copyright © 2009 by Pearson Education, Inc.

Learning Check What is the molar mass of each of the following? A. K2O B. Al(OH)3

Learning Check Prozac, C17H18F3NO, is an antidepressant that inhibits the uptake of serotonin by the brain. What is the molar mass of Prozac? 1) 40.1 g/mole 2) 262 g/mole 3) 309 g/mole

Molar Mass Factors Molar mass conversion factors are fractions (ratios) written from the molar mass. relate grams and moles of an element or compound. for methane, CH4, used in gas stoves and gas heaters is 1 mole of CH4 = 16.0 g (molar mass equality) Conversion factors: 16.0 g CH4 and 1 mole CH4 1 mole CH4 16.0 g CH4

Learning Check Acetic acid, C2H4O2, gives the sour taste to vinegar. Write two molar mass conversion factors for acetic acid. Copyright © 2009 by Pearson Education, Inc.

Calculations Using Molar Mass Molar mass factors are used to convert between the grams of a substance and the number of moles. Molar mass factor Grams Moles

Moles to Grams Aluminum is often used to build lightweight bicycle frames. How many grams of Al are in 3.00 mole of Al? Molar mass equality: 1 mole of Al = 27.0 g of Al Setup with molar mass as a factor: 3.00 mole Al x 27.0 g Al = 81.0 g of Al 1 mole Al molar mass factor for Al

Learning Check Allyl sulfide, C6H10S, is a compound that has the odor of garlic. How many moles of C6H10S are in 225 g? Copyright © 2009 by Pearson Education, Inc.

Grams, Moles, and Particles A molar mass factor and Avogadro’s number convert…

Learning Check How many H2O molecules are in 24.0 g of H2O? 1) 4.52 x 1023 H2O molecules 2) 1.44 x 1025 H2O molecules 3) 8.03 x 1023 H2O molecules

Learning Check If the odor of C6H10S can be detected from 2 x 10-13 g in 1 liter of air, how many molecules of C6H10S are present?

Chapter 5 Chemical Quantities and Reactions 5.3 Chemical Changes Copyright © 2009 by Pearson Education, Inc.

Physical Change In a physical change, the state, shape, or size of the material changes. the identity and composition of the substance do not change. Copyright © 2009 by Pearson Education, Inc.

Chemical Change In a chemical change, reacting substances form new substances with different compositions and properties. a chemical reaction takes place. Copyright © 2009 by Pearson Education, Inc.

Some Examples of Chemical and Physical Changes Copyright © 2009 by Pearson Education, Inc.

Learning Check Classify each of the following as a 1) physical change or 2) chemical change. A. ____Burning a candle. B. ____Ice melting on the street. C. ____Toasting a marshmallow. D. ____Cutting a pizza. E. ____Polishing a silver bowl.

Chemical Reaction In a chemical reaction a chemical change produces one or more new substances. there is a change in the composition of one or more substances. Copyright © 2009 by Pearson Education, Inc.

Chemical Reaction In a chemical reaction old bonds are broken and new bonds are formed. atoms in the reactants are rearranged to form one or more different substances.

Chemical Reaction In a chemical reaction the reactants are Fe and O2. the new product Fe2O3 is called rust. Copyright © 2009 by Pearson Education, Inc.

Chapter 5 Chemical Quantities and Reactions 5.4 Chemical Equations Copyright © 2009 by Pearson Education, Inc.

Chemical Equations A chemical equation gives the formulas of the reactants on the left of the arrow. the formulas of the products on the right of the arrow. Reactants Product O2 (g) CO2 (g) C(s) Copyright © 2009 by Pearson Education, Inc.

Symbols Used in Equations Symbols in chemical equations show the states of the reactants. the states of the products. the reaction conditions. TABLE

Chemical Equations are Balanced In a balanced chemical reaction no atoms are lost or gained. the number of reacting atoms is equal to the number of product atoms. Copyright © 2009 by Pearson Education, Inc.

A Balanced Chemical Equation In a balanced chemical equation, the number of each type of atom on the reactant side is equal to the number of each type of atom on the product side. numbers called coefficients are used in front of one or more formulas to balance the number of atoms. Al + S Al2S3 Not Balanced 2Al + 3S Al2S3 Balanced using coefficients 2 Al = 2 Al Equal number of Al atoms 3 S = 3 S Equal number of S atoms

A Study Tip: Using Coefficients When balancing a chemical equation, use one or more coefficients to balance atoms. never change the subscripts of any formula. N2 + O2 NO Not Balanced N2 + O2 N2O2 Incorrect formula N2 + O2 2NO Correctly balanced using coefficients

Learning Check State the number of atoms of each element on the reactant side and the product side for each of the following balanced equations. A. P4(s) + 6Br2(l) 4PBr3(g) B. 2Al(s) + Fe2O3(s) 2Fe(s) + Al2O3(s)

Learning Check Determine if each equation is balanced or not. A. Na(s) + N2(g) Na3N(s) B. C2H4(g) + H2O(l) C2H6O(l)

Steps in Balancing an Equation To balance the following equation, Fe3O4(s) + H2(g) Fe(s) + H2O(l) work on one element at a time. use only coefficients in front of formulas. do not change any subscripts. Fe: Fe3O4(s) + H2(g) 3Fe(s) + H2O(l) O: Fe3O4(s) + H2(g) 3Fe(s) + 4H2O(l) H: Fe3O4(s) + 4H2(g) 3Fe(s) + 4H2O(l)

Balancing Chemical Equations 1. Write the equation with the correct formulas. NH3(g) + O2(g) NO(g) + H2O(g) 2. Determine if the equation is balanced. No, H atoms are not balanced. 3. Balance with coefficients in front of formulas. 2NH3(g) + O2(g) 2NO(g) + 3H2O(g) Double the coefficients to give even number of O atoms. 4NH3(g) + 7O2(g) 4NO(g) + 6H2O(g)

Balancing Chemical Equations 4. Check that atoms of each element are equal in reactants and products. 4NH3(g) + 5O2(g) 4NO(g) + 6H2O(g) 4 N (4 x 1 N) = 4 N (4 x 1 N) 12 H (4 x 3 H) = 12 H (6 x 2 H) 10 O (5 x 2 O) = 10 O (4 O + 6 O)

Equation for a Chemical Reaction Copyright © 2009 by Pearson Education, Inc.

Checking a Balanced Equation Copyright © 2009 by Pearson Education, Inc. Reactants Products 1 C atom = 1 C atom 4 H atoms = 4 H atoms 4 O atoms = 4 O atoms

Learning Check Check the balance of atoms in the following: Fe3O4(s) + 4H2(g) 3Fe(s) + 4H2O(l) A. Number of H atoms in products. 1) 2 2) 4 3) 8 B. Number of O atoms in reactants. C. Number of Fe atoms in reactants. 1) 1 2) 3 3) 4

Learning Check Balance each equation and list the coefficients in the balanced equation going from reactants to products: A. __Mg(s) + __N2(g) __Mg3N2(s) 1) 1, 3, 2 2) 3, 1, 2 3) 3, 1, 1 B. __Al(s) + __Cl2(g) __AlCl3(s) 1) 3, 3, 2 2) 1, 3, 1 3) 2, 3, 2

Equations with Polyatomic Ions 2Na3PO4(aq) + 3MgCl2 (aq) Mg3 ( PO4(s) + 6NaCl(aq) Copyright © 2009 by Pearson Education, Inc.

Balancing with Polyatomic Ions Na3PO4(aq) + MgCl2(aq) Mg3(PO4)2(s) + NaCl(aq) Balance PO43- as a unit 2Na3PO4(aq) + MgCl2(aq) Mg3(PO4)2(s) + NaCl(aq) 2 PO43- = 2 PO43- Check Na + balance 6 Na+ = 6 Na+ Balance Mg and Cl 2Na3PO4(aq) + 3MgCl2(aq) Mg3(PO4)2(s) + 6NaCl(aq) 3 Mg2+ = 3 Mg2+ 6 Cl- = 6 Cl-

Learning Check Balance and list the coefficients from reactants to products. A. __Fe2O3(s) + __C(s) __Fe(s) + __CO2(g) 1) 2, 3, 2, 3 2) 2, 3, 4, 3 3) 1, 1, 2, 3 B. __Al(s) + __FeO(s) __Fe(s) + __Al2O3(s) 1) 2, 3, 3, 1 2) 2, 1, 1, 1 3) 3, 3, 3, 1 C. __Al(s) + __H2SO4(aq) __Al2(SO4)3(aq) + __H2(g) 1) 3, 2, 1, 2 2) 2, 3, 1, 3 3) 2, 3, 2, 3