Presentation on theme: "Chemical Equations & Reactions"— Presentation transcript:
1 Chemical Equations & Reactions Chemical Reaction - Study Questions1. What is a chemical reaction?2. What is evidence a reaction has occurred?3. What is a chemical equation?4. Define reactants.5. Define products.6. Define catalyst.7. What information is found in an equation?8. What symbols are used to represent the states of matter?9. What is the meaning of “aq”?10. How do you indicate a catalyst is being used in a reaction?11. What is activation energy?12. What the three things does conservation of matter require of chemical equations?13. What is the procedure for balancing a chemical equation?14. Balance the equation for the reaction of magnesium chloride and silver nitrate to form magnesium nitrate and silver chloride.15. What is a synthesis reaction?16. How is a combustion reaction related to a synthesis reaction?17. What type of reaction is an explosion?18. Compare decomposition and dissociation.19. What determines whether one metal will replace another in a single displacement reaction?20. What is the general form of a double displacement reaction?21. What type of reaction is each of these?2Na(s) + Cl2(g) 2NaCl(s)PCl5(s) PCl3(s) + Cl2(g)2Al(s) + Fe2O3(s) 2Fe(s) + Al2O3(s)C6H12O6(s) + 6O2(g) 6CO2(g) + 6H2O(l)BaCl2(aq) + H2SO4(aq) 2HCl(aq) + BaSO4(s)22. What is the oxidation number of an element?23. What is the oxidation number of the fluorine ion?24. What is the sum of the oxidation numbers in a compound?31. Can a redox reaction form a molecule? Explain your answer.
2 Chemical Reactions You should be able to Classify reactions by type. Write a balanced molecular equation, complete ionic equation,and a net ionic equation.Balance oxidation-reduction reactions.Predict if a precipitate will form using the solubility rules.Predict products of reactions given the chemical names of thereactants.What you should learn:In chemical change atoms are rearranged but no atoms are created and none are destroyedChemical equations are symbolic representations of what is happening at the molecular level and are used to communicate the conditions under which a reaction proceeds, the products and amount of energy that results, and allow for predictions to be made.More Specifically...:Classify those equations that come under the heading of synthesis, decomposition, single replacement, double replacement, neutralization, oxidation/ reduction and combustionIdentify and name acids and basesUse principle of conservation of mass to balance a reactionFrom a written description of a reaction write a balanced reaction using correct state symbolsShow that the conservation of mass is true for a balanced reactionPredict the products of chemical reactions (including state symbols) when given the reactants.Use an activity series to predict the spontaneity of reactions.Use solubility rules to predict the formation of a precipitateDefine oxidation and reduction, and identify any species undergoing oxidation or reduction, and identify the oxidizing and reducing agentsWrite half reactions for single replacement reactions (monoatomic ions only)Fast Track to a 5 (page 61)To know how to calculate the molecular mass of a covalent compound and the formula mass of an ionic compoundTo be able to use the concepts of the mole and molar mass to calculate the number of atoms, molecules, or formula units in a sample of a substanceTo be able to determine the empirical formula of a compound from its composition by massTo know how to derive the molecular formula of a compound from its empirical formulaTo be able to describe a chemical reactionTo know how to calculate the quantities of compounds produced or consumed in a chemical reactionTo identify fundamental types of chemical reactionsTo begin to predict the types of chemical reactions that substances undergo
3 Organize Your Thoughts ChemicalreactionsChemicalequationsChemicalequationsTo identify the reactants and products in a chemical equation.To balance a chemical equation with coefficients.To identify synthesis (combination), decomposition, and combustion reactions.To identify single-replacement reactions.To identify double-replacement reactions.To predict the products of a reaction.SynthesisDecompositionSingle replacementDouble replacementCombustionOx-RedoxWriting equationsBalancing equationsPredicting productsfrom reactants
4 Describing a Chemical Reaction Indications of a Chemical ReactionEvolution of heat, light, and/or soundProduction of a gasFormation of a precipitateColor changeObjective:To state four observations that are evidence for a chemical reaction.Photo of precipitate:
5 Signs of Chemical Reactions There are five main signs that indicate a chemical reaction has taken place:releaseinputchange in colorchange in odorproduction of newgases or vaporinput or releaseof energydifficult to reverse
6 Chemical Equations Depict the kind of reactants and products aluminum oxideDepict the kind of reactants and productsand their relative amounts in a reaction.reactantsproduct4 Al(s) O2(g) Al2O3(s)A chemical equation is an expression that gives the identities and quantities of the substances in a chemical reactionChemical formulas and other symbols are used to indicate the starting material(s) or reactant(s), which are written on the left side of the equation, and the final compound(s) or product(s), which are written on the right side. An arrow, read as yields or reacts to form, points from the reactants to the products.Abbreviations are added in parentheses as subscripts to indicate the physical state of each species:—(s) for solid, (l) for liquid, (g) for gas, and (aq) for an aqueous solution.A balanced chemical equation is when both the numbers of each type of atom and the total charge are the same on both sides. A chemical reaction represents a change in the distribution of atoms but not in the number of atoms.The letters (s), (g), and (l) are thephysical states of compounds.The numbers in the front are calledstoichiometric coefficients.
7 Chemical Equations 4 Al(s) + 3 O2(g) 2 Al2O3(s) aluminum oxidesandpaper4 Al(s) O2(g) Al2O3(s)4 g Al g O2 yield 2 g Al2O3This equation means:4 Al atoms O2 molecules yield 2 molecules of Al2O3or4 Al moles O2 moles yield 2 moles of Al2O34 mol3 mol2 mol108 g g = g
8 Chemical Equations Because the same atoms are present in a reaction at the beginning (reactants)and at the end (products), the amountof matter in a system does not change.The Law of Conservation of MatterLaw of Conservation of Matter means that nothing is “lost” or “stolen”. In the real world retail theft costs business lots (much of the theft is actually employee theft)!20%100%ChemicalFactory100%80%Kotz web
9 Chemical EquationsBecause of the principle of the conservation of matter,An equation must be balanced.It must have the same number of atomsof the same kind on both sides.Lavoisier, 1788
10 Characteristics of Chemical Equations The equation must represent known facts.The equation must contain the correct formulas for the reactants and products.The law of conservation of mass must be satisfied.
11 Chemical EquationsReactants – the substances that exist before a chemical change (or reaction) takes place.Products – the new substance(s) that are formed during the chemical changes.CHEMICAL EQUATION indicates the reactants and products of a reaction.Objectives:To identify seven elements that occur naturally as diatomic molecules, H2, N2, O2, F2, Cl2, Br2, I2. [HOBrFINCL twins or BrINClHOF brothers]To write a chemical equation from the description of a chemical reaction.REACTANTS PRODUCTS
12 Additional Symbols Used in Chemical Equations “Yields”; indicates result of reactionUsed to indicate a reversible reactionA reactant or product in the solid state;also used to indicate a precipitateAlternative to (s), but used only to indicate a precipitateA reactant or product in the liquid stateA reactant or product in an aqueous solution(dissolved in water)A reactant or product in the gaseous state(s)(l)(aq)(g)
13 Additional Symbols Used in Chemical Equations Alternative to (g), but used only to indicate a gaseous productReactants are heatedPressure at which reaction is carried out, in this case 2 atmPressure at which reaction is carried out exceeds normalatmospheric pressureTemperature at which reaction is carried out, in this case 0 oCFormula of catalyst, in this case manganese (IV) oxide,used to alter the rate of the reactionD2 atmpressure0 oCMnO2
14 Word EquationsA WORD EQUATION describes chemical change using the names of the reactants and products.Write the word equation for the reaction of methane gas with oxygen gas to form carbon dioxide and water.methane oxygencarbon dioxide waterReactantProductCH4+2O2CO2+2H2O
16 Balancing Chemical Equations Balanced Equation – one in which the number of atoms of each element as a reactant is equal to the number of atoms of that element as a productWhat is the relationship between conservation of mass andthe fact that a balanced equation will always have the samenumber of atoms of each element on both sides of an equation?Objective:To write balanced chemical equations by inspection.Balanced chemical equation– Provides qualitative information about the identities and physical states of the reactants and products– Provides quantitative information because it tells the relative amounts of reactants and products consumed or produced in the reaction– The number of atoms, molecules, or formula units of a reactant or product in a balanced chemical equation is the coefficient of that species– Mole ratio of two substances in a chemical reaction is the ratio of their coefficients in the balanced chemical equationDetermine whether the following equation is balanced.2 Na + H2O 2 NaOH + H22 Na H2O 2 NaOH + H2
17 Balancing Chemical Equations Write a word equation for the reaction.Write the correct formulas for all reactants and products.Determine the coefficients that make the equation balance.
18 Balancing Chemical Equations An important point to remember2 NO(g) + O2(g) 2NO2(g)The 2 to the left of NO(g) and NO2(g) refers to the number of molecules present in the balanced equation.It is a “multiplier” for every atom in the molecule.The subscript 2 in O2 (g) and NO2(g) refers to the numberof atoms of this type that are present in each molecules(or ionic compound).
20 Balancing Chemical Equations Balancing Equations (visual) Balancing Chemical EquationsKeys (visual)
21 Write a balanced equation for the reaction between chlorine and sodium bromide to produce bromine and sodium chloride.1) Write a word equation for the reaction.chlorine sodium bromide bromine + sodium chloride2) Write the correct formulas for all reactants and products.Cl NaBr Br NaCl3) Determine the coefficients that make the equation balance.Cl NaBr Br NaCl
22 Write the balanced equation for the reaction between aluminum sulfate and calcium chloride to form a white precipitate of calcium sulfate.1) Write a word equation for the reaction.??aluminum sulfate + calcium chloride calcium sulfate+ aluminum chloride2) Write the correct formulas for all reactants and products.Al2(SO4) CaCl CaSO AlCl33) Determine the coefficients that make the equation balance.Al2(SO4) CaCl CaSO AlCl3
23 CH4 + 2 O2 CO2 + 2 H2O Reactants Products 1 C atom 1 C atom 4 H atoms H atoms4 O atoms O atoms