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6-1 Representing Chemical Changes
Chemical equations are used to represent chemical reactions Reactants are the starting substances and products are the substances formed in chemical reactions Reactant(left side) -----> Product(right side)(-----> reads yields) (g)=gas (l)=liquid (cr)=crystal (aq)=a water solution 6-2 Balancing Equations 1-Determine the reactants and the products 2-assemble the parts of the chemical equation 3-balance the equation balanced equations have the same kind and number of atoms on each side. coefficients NOT subscripts may be changed to balance an equation 6-3 Classifying Chemical Changes Single Replacement Double Replacement Decomposition Synthesis Combustion Under normal conditions, the oxidation of a hydrocarbon produces carbon dioxide and water. 6-4 Mass Mass Relationships 1-write the balanced equation 2-find the number of moles of given substance and required substance 3-convert the grams of given substance to moles 4-determine the mole ratio from the balanced equation 5-express the moles of required substance in terms of grams Stoichiometry is the quantitative study of chemical reactions The balanced equation indicates the relative number of moles of reactants and products in the reaction and is used as the basis for solving mass-mass problems The actual amount of product obtained in a reaction is often expressed as a percentage of the theoretical amount. 6-5 Energy ad Chemical Change If energy is absorbed in a reaction, the reaction is endothermic If energy is released in a reaction, the reaction is exothermic Chemical changes are accompanied by a change in energy The minimum amount of energy required to start a reaction is the activation energy for that reaction. |
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