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Answer» Step 1 \tThe unbalanced equation must be obtained from the chemical formulae of the reactants and the products (if it is not already provided).\tThe chemical formula of propane is C3H8. It burns with oxygen (O2) to form carbon dioxide (CO2) and water (H2O)\tThe unbalanced chemical equation can be written as C3H8 + O2 → CO2 + H2O\tStep 2\tThe total number of atoms of each element on the reactant side and the product side must be compared. For this example, the number of atoms on each side can be tabulated as follows.\tChemical Equation: C3H8 + O2 → CO2 + H2OReactant SideProduct Side3 Carbon atoms from C3H81 Carbon atom from CO28 Hydrogen atoms from C3H82 Hydrogen atoms from H2O2 Oxygen atoms from O23 Oxygen atoms, 2 from CO2 and 1 from H2O\t\tStep 3\tNow, stoichiometric coefficients are added to molecules containing an element which has a different number of atoms in the reactant side and the product side.The coefficient must balance the number of atoms on each side.Generally, the stoichiometric coefficients are assigned to hydrogen and oxygen atoms last.Now, the number of atoms of the elements on the reactant and product side must be updated.It is important to note that the number of atoms of an element in one species must be obtained by multiplying the stoichiometric coefficient with the total number of atoms of that element present in 1 molecule of the species.For example, when the coefficient 3 is assigned to the CO2 molecule, the total number of oxygen atoms in CO2 becomes 6. In this example, the coefficient is first assigned to carbon, as tabulated below.\t\tChemical Equation: C3H8 + O2 → 3CO2 + H2OReactant SideProduct Side3 Carbon atoms from C3H83 Carbon atoms from CO28 Hydrogen atoms from C3H82 Hydrogen atoms from H2O2 Oxygen atoms from O27 Oxygen atoms, 6 from CO2 and 1 from H2O\t\tStep 4\tStep 3 is repeated until all the number of atoms of the reacting elements are equal on the reactant and product side. In this example, hydrogen is balanced next. The chemical equation is transformed as follows.\tb\tChemical Equation: C3H8 + O2 → 3CO2 + 4H2OReactant SideProduct Side3 Carbon atoms from C3H83 Carbon atoms from CO28 Hydrogen atoms from C3H88 Hydrogen atoms from H2O2 Oxygen atoms from O210 Oxygen atoms, 6 from CO2 and 4 from H2O\t\tNow that the hydrogen atoms are balanced, the next element to be balanced is oxygen. There are 10 oxygen atoms on the product side, implying that the reactant side must also contain 10 oxygen atoms.\tEach O2 molecule contains 2 oxygen atoms. Therefore, the stoichiometric coefficient that must be assigned to the O2 molecule is 5. The updated chemical equation is tabulated below.\tChemical Equation: C3H8 + 5O2 → 3CO2 + 4H2OReactant SideProduct Side3 Carbon atoms from C3H83 Carbon atoms from CO28 Hydrogen atoms from C3H88 Hydrogen atoms from H2O10 Oxygen atoms from O210 Oxygen atoms, 6 from CO2 and 4 from H2O\t\tStep 5\tOnce all the individual elements are balanced, the total number of atoms of each element on the reactant and product side are compared once again.If there are no inequalities, the chemical equation is said to be balanced.In this example, every element now has an equal number of atoms in the reactant and product side.Therefore, the balanced chemical equation is C3H8 + 5O2 → 3CO2 + 4H2O.\t\t\xa0\t
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