Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Do Now!!! What is the name of NaOH? Sodium Hydroxide What is the formula of copper (II) chloride? CuCl2 Chapter 7 Chemical Reactions Objectives • Interpret chemical equations in terms of reactants, products, and conservation of mass. • Balance chemical equations by manipulating coefficients. Reactants A Substance that undergoes change in a chemical reaction. Products New substances formed as a result of a chemical reaction. Chemical Equation A representation of a chemical reaction in which the reactants and products are expressed as formulas. Reactants Products Example Reactants Products Carbon + Oxygen Carbon dioxide C + O2 CO2 Conservation of Mass Mass is neither created nor destroyed in a chemical reaction, it just changes forms. Coefficients Number that appear before a formula in a chemical equation to show the relative proportions of each reactant and product. Note: Coefficients are necessary to show that mass is conserved during a reaction, a chemical equation must be balanced. Balancing Equations Important: You should never change the subscripts in a formula!!! Changing the formula changes the identity of that reactant or product. Balancing Equations 1. Count the number of atoms of each element on each side of the equation. 2. Change one or more coefficients until the equation is balanced. 3. Once the equation is balanced, recount the number of atoms of each element to ensure that they are the same on each side. Balancing Equations Example N2H4 + O2 N=2 O=2 H=4 N2 + H2O N=2 H=2 O=1 N2H4 + O2 N=2 O=2 H=4 N2 + 2H2O N=2 H=4 O=2 Do Now!!! For each type of atom in copper (II) nitrate, determine the number of atoms that are present? Cu(NO3)2 Cu = 1 N=2 O=6 Objectives • Interpret chemical equations in terms of reactants, products, and conservation of mass. • Balance chemical equations by manipulating coefficients. Balancing Equations Examples Cl2 Cl2 HCl 2HCl + HCl + 2HCl H2 H2 + O2 + 3O2 CO2 2CO2 H2 H2 Mg Mg C2H4 C2H4 + + + + MgCl2 MgCl2 + H2O + 2H2O Do Now!!! Balance the following chemical equation: Na2O + H2O NaOH Na2O + H2O 2NaOH Mole An amount of a substance that contains approximately 6.02 1023 atoms, molecules, or ions of the substance. Because chemical reactions often involve large numbers of small particles, chemists use a counting unit called the mole to measure amounts of a substance. Molar Mass The mass of one mole of a substance. For an element: the molar mass is the same as its atomic mass expressed in grams. For a compound: Add up the atomic masses of its component atoms, then expressing the sum in grams. Calculating Molar Mass Carbon dioxide (CO2) 1. Calculate the molar mass of C: Molar Mass of C = 12.011 1 = 12.011 2. Calculate the molar mass of O: Molar Mass of O = 15.999 2 = 31.998 3. Calculate the total molar mass of CO2: Molar Mass of CO2 = 12.011 + 31.998 Molar Mass of CO2 = 44.009 Molar Mass Examples 1. Water (H2O) = 18.0148 2. Magnesium oxide (MgO) = 40.304 3. Sodium Chloride (NaCl) = 58.443 4. Ammonia (NH3) = 17.0307 Do Now!!! Calculate the molar mass of the following: NH4Cl 53.50 g Mg3(PO4)2 262.87 g Copper (II) fluoride CuF2 101.54 g Objective • Convert between moles and mass of a substance using molar mass. Mole - Mass Conversions Molar Mass Conversion Factors: Molar mass of sample 1 mole of sample 1 mole of sample Molar mass of sample Mole - Mass Conversions Molar Mass Conversion Factors: Molar mass of sample 44.009 g of CO2 = 1 mole of sample 1 mole of CO2 1 mole of sample 1 mole of CO2 = Molar mass of sample 44.009 g of CO2 Mole - Mass Calculations Molar Mass Conversion Factor: 44.009 g of CO2 1.25 mol CO2 1 mole of CO2 1 mole of CO2 55.0 g CO2 44.009 g of CO2 Do Now!!! Calculate the molar mass of the following: NaBr 102.90 g Na2CO3 134.06 g Aluminum sulfide Al2S3 150.14 g Objective • Convert between moles and mass of a substance using molar mass. Mole - Mass Calculations Molar Mass Conversion Factor: 44.009 g of CO2 1.25 mol CO2 = 55.0 g CO2 1 mole of CO2 1 mole of CO2 55.0 g CO2 = 1.25 mol CO2 44.009 g of CO2 Mole - Mass Examples 1. 2 mol H2O = 36.0296 g H2O 2. 3.1 mol MgO = 124.9424 g MgO 3. 16.2 g NaCl = 0.277 mol NaCl 4. 30.8 g NH3 = 1.808 mol NH3 Chemical Calculations In a chemical reaction, the mass of a reactant or product can be calculated by using a balanced chemical equation and molar masses of the reactants and products. Using Molar Ratios 2 H2 + O2 2 H2O Conversion Factors for O2 and H2O: 1 mole O2 2 mol H2O or 2 mol H2O 1 mole O2 Do Now!!! 1. 4.6 mol HC2H3O2 = 276.28 g HC2H3O2 2. 143.6 g CH3CH2OH = 3.12 mol CH3CH2OH Objective • Classify chemical reactions as synthesis, decomposition, single-replacement, double-replacement, or combustion reactions. General Types of Reactions 1. 2. 3. 4. 5. Synthesis Reaction Decomposition Reactions Single-replacement Reactions Double-replacement Reactions Combustion Reactions Synthesis Reaction A chemical reaction in which two or more substances react to form a single substance. Example of Synthesis Reactions 2 Na + Cl2 2 NaCl 2 H2 + O2 2 H2O Decomposition Reaction A chemical reaction in which a compound breaks down into two or more simpler substances. Examples of Decomposition Reactions 2 H2O 2 H2 + O2 CaCO3 CaO + CO2 Single-Replacement Reaction A chemical reaction in which one element takes the place of another element in a compound. Examples of Single-Replacement Reactions Cu + 2 AgNO3 Cu(NO3)2 + 2 Ag 2 K + 2 H2O H2 + 2 KOH 2 K + 2 HOH H2 + 2 KOH Double-Replacement Reaction A chemical reaction in which two compounds exchange positive ions and form two new compounds. Examples of Double-Replacement Reactions Pb(NO3)2 + KI PbI2 + 2 KNO3 CaCO3 + 2 HCl CaCl2 + H2CO3 Do Now!!! Balance the following chemical equation: Ba3N2 + H2O Ba(OH)2 + NH3 Ba3N2 + 6 H2O 3 Ba(OH)2 + 2 NH3 (NH4)2Cr2O7 Cr2O3 + N2 + H 2O (NH4)2Cr2O7 Cr2O3 + N2 + 4 H2O Objective • Classify chemical reactions as synthesis, decomposition, single-replacement, double-replacement, or combustion reactions. Combustion Reaction A chemical reaction in which a substance reacts rapidly with oxygen, often producing heat and light. Example of a Combustion Reaction CH4 + 2 O2 CO2 + 2 H2O Material for Chpt. 7 Exam Chemical equations Balancing chemical equations Molar mass Mass – mole conversions Type of chemical reactions Do Now!!! 1. 2.67 mol Pb(NO3)4 = 1215.49 g Pb(NO3)4 2. 285.26 g PCl5 = 1.37 mol PCl5 Objectives • Describe the energy changes that takes place during chemical reactions. • Classify chemical reactions as exothermic or endothermic. • Explain how energy is conserved during chemical reactions. Oxidation-Reduction Reaction A chemical reaction in which electrons are transferred from one reactant to another. Chemical Energy The energy stored in the chemical bonds within a substance. Chemical Reactions Chemical reactions involve the breaking of chemical bonds in the reactants and the formation of chemical bonds in the products. Chemical Reactions Breaking bonds: Requires energy Forming bonds: Releases energy Exothermic Reaction A chemical reaction that releases energy to its surroundings. Exothermic Reaction The combustion of propane: C3H8 + 5 O2 3 CO2 + 4 H2O + 2220 kJ Endothermic Reaction A chemical reaction that absorbs energy from its surroundings. Endothermic Reaction The decomposition of mercury(II) oxide: 2 HgO + 181.7 kJ 2 Hg + O2 Conservation of Energy The total amount of energy before and after the reaction is the same. Objectives • Explain what a reaction rate is. • Describe the factors affecting chemical reaction rates. Reaction Rate The rate at which reactants change into products over time. Catalyst A substance that affects the rate of a chemical reaction without being used up in the reaction. Objectives • Identify and describe physical and chemical equilibria. • Describe the factors affecting chemical equilibrium. Equilibrium A state in which the forward and reverse paths of a physical or chemical change take place at the same rate. Reversible Reaction A chemical reaction in which the conversion of reactants into products and the conversion of products into reactants happens at the same time. Balancing Equations Examples Cl2 HCl HCl H2 + O2 CO2 H2 Mg C2H4 + + + MgCl2 + H2O