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Chapter 8 Chemical Reactions

Chapter 8 Chemical Reactions. Chemistry by Addison - Wesley. 8.1 Describing Chemical Change. Word Equations In a chemical reaction, one or more substances change into one or more new substances Reactants Products

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Chapter 8 Chemical Reactions

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  1. Chapter 8 Chemical Reactions Chemistry by Addison - Wesley

  2. 8.1 Describing Chemical Change • Word Equations • In a chemical reaction, one or more substances change into one or more new substances • Reactants Products • Important to note that in a chemical reaction the atoms are neither created or destroyed; just rearranged

  3. Chemical Equations • Chemical equation is similar to a word equation only chemical symbols represent substances • Skeleton equation represents the compounds without a quantity • State of matter can also be added to a skeleton equation • H2 (g) + O2 (g) H2O (l)

  4. Balancing Equations • Rules for Balancing Equations • Determine the correct formulas for the reaction • Write the formula with the reactants on the left and the products on the right • Count the number of atoms of each element on each side • Balance the elements one at a time using coefficients • Check each atom to make sure that it is balanced • Make sure the coefficients are in the lowest possible ratio

  5. 8.2 Types of Chemical Reactions • Classifying reactions • Five Categories • Synthesis • Decomposition • Single-displacement • Double-displacement • Combustion

  6. Synthesis Reactions • In a synthesis reaction, two or more substances combine to form a single substance • Two or more reactants • One product • H2 + O2 -> H2O

  7. Decomposition Reactions • In a decomposition reaction, one substance breaks down into two or more substances • One Reactant • Two or more products • H2O -> H2 + O2 • Often require heat or some sort of energy source to break down bonds in the compound

  8. Single-Displacement Reactions • In a single-displacement reaction, one element replace another in a compound • Two reactants • Two products • Na + HCl -> H2 + NaCl • Normally, the replacement occurs at the cation spot

  9. Double-Displacement Reactions • In a double-displacement reactions, two compounds exchange cations • Two reactants • Two products • NaOH + HCl -> H(OH) + NaCl • In most cases, one of the following will occur in a double-replacement reaction: 1) a precipitate forms, 2) a gas forms, or 3) a molecular compound forms

  10. Combustion Reactions • In combustion reactions, a compound reacts with oxygen often to produce heat or light • One of the reactants will always be oxygen • A hydrocarbon is often the other reactant • Combustion of a hydrocarbon will produce H2O and CO2 • C2H6 + O2 -> H2O + CO2 + heat

  11. 8.3 Reactions in Aqueous Solutions • Net Ionic Equation • In an aqueous solution, compounds ionize into solution • Ions that are on both sides of the equation are called spectator ions • These ions cancel out of the equation • Net Ionic Equation

  12. Predicting the Formation of a Precipitate • Solubility Rules for Ionic Compounds • Salts of alkali metals and ammonia - soluble (exceptions some lithium compounds) • Nitrate salts and chlorate salts - soluble (few exceptions) • Sulfate salts - soluble (Compounds of Pb, Ag, Hg, Ba, Sr, and Ca are exceptions) • Chloride salts - soluble (Ag and some Hg and Pb are exceptions) • Carbonates, phosphates, chromates, sulfides, and hydroxides - insoluble (Alkali metals and ammonia)

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