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Balancing Equations. When writing a chemical equation, the law of the conservation of mass must be observed. Conservation of Mass in a chemical reaction , the mass of the products equals the mass of the reactants . The # of atoms in the reactants = the # of atoms in the products.
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When writing a chemical equation, the law of the conservation of mass must be observed • Conservation of Mass • in a chemical reaction, the mass of the products equals the mass of the reactants. • The # of atoms in the reactants = the # of atoms in the products
Coefficient – the whole number out front of the formula- tells you how many of each molecule • Subscript– small number to the bottom right of an element- tells you how many atoms of that element are in the molecule. Ex. 2H2(g) + O2 2H2O
Combustion of Methane • Methane gas burns to produce carbon dioxide gas and liquid water • Whenever something burns it combines with O2 • Write the equation above:
Steps for Writing Equations • Use proper formulas for each reactant and product • Proper equations should be balanced • Count the number of atoms of each element on the reactants side • Count the number of atoms of each element on the products side • Balance atoms by using coefficients -- Check your work by counting atoms of each element.
Balance by Inspection • Polyatomic ions may be counted as one “element” if it does not change in the reaction Al + FeSO4 Al2(SO4)3 + Fe If an element appears in more than one compound on the same side, count each separately and add CO + O2 CO2
Pick an element to balance • Use a table if necessary to keep track of your elements • Continue to adjust coefficients until balanced. C O C O # # # #