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CHEMICAL EQUATIONS

CHEMICAL EQUATIONS. LAW OF CONSERVATION OF MASS BALANCING FOR CONSERVATION OF MASS TYPES OF CHEMICAL REACTIONS. Levoisier And Balancing. Levoisier summarizied his observations of chemical change by stating, among other things, that during a chemical change matter is conserved.

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CHEMICAL EQUATIONS

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  1. CHEMICAL EQUATIONS LAW OF CONSERVATION OF MASS • BALANCING FOR CONSERVATION OF MASS • TYPES OF CHEMICAL REACTIONS

  2. Levoisier And Balancing Levoisier summarizied his observations of chemical change by stating, among other things, that during a chemical change matter is conserved. • That is, matter is neither created or destroyed. • The mass of the reactants equals the mass of the products.

  3. Comprehension A “balanced” equation has the same number of atoms of each element in both the reactant and product sides of the equation. Reactants Products C + O2 CO2 Two elements make a compound (addition ) Balance: (1) carbon atom (1) carbon atom (2) oxygen atoms (2) oxygen atoms

  4. Consolidation Reactants Products 2H2O 2H2 + O2 a compound makes Two elements (decomposition ) Balance: (4) hydrogen atoms (4) hydrogen atoms (2) oxygen atoms (2) oxygen atoms

  5. A Three Step Approach • First a word equation is written to summarize the reaction in words. hydrogen + oxygen water The above is read as: Hydrogen gas molecules react with oxygen gas molecules to produce water molecules • Then a skeleton equation is written with all the correct formulas for the substances. H2(g) + O2 (g)H2O(l) • Then the equation is balanced for conservation of mass. (Large multipliers are placed in front of substances to balance the equation) • 2H2 + O2 2H2O

  6. Mechanics of Balancing Where do you start? • To start avoid elements which occur more than once on a side. Start with those occurring only once on a side • Pb in PbO2 +HBr-> H2O + PbBr2 + Br2 • Balance complex ions as units rather than individual elements whenever possible. • e.g. NO3, SO4 • Al2(SO4)3+ 3Ba(NO3)2->2Al(NO3)3 +3BaSO4 • Avoid elements which occur by themselves until last. • Be methodical. Don’t jump around balancing a bit here and there.

  7. Types of Chemical Reactions Reactants Products C + O2 CO2 (addition ) two elements make a compound 2 H2O2H2 + O2(decomposition) a compound make two elements AgNO3 + Cu Cu NO3 + Ag (single replacement) compound reacts with element to as metal ions switched places AgNO3 + Cu SO4 Cu NO3 + AgSO4 (double replacement) compound reacts with compound asmetal ions switch places CH4 + 2O2 CO2 + 2H2O (hydrocarbon combustion) hydrocarbon reacts with oxygen to make carbon dioxide and water

  8. Conclusions • The types of chemical reactions can be used to predict possible products given the reactants. • The reaction is then done and the products are observed to verify the prediction. • What evidence would you expect to verify in the following? • AgNO3 + Cu Cu NO3 + Ag (replacement) • __HCl + Mg MgCl2 + H2 (replacement) • Complete this skeleton equation: • CuSO4 + Fe

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