1. Balancing Equations

2. Balancing chemical equations is necessary so that they obey the law of conservation of mass. Remember, in Ch. R, atoms are not created or destroyed; they are simply rearranged. Balanced equation – a chemical equation in which mass is conserved; each side of the equation has the same number of atoms of each elements.

3. Balancing Equations 1. Formulas must be correct before balancing 2. Goal: to have equal numbers of each type of atom on both sides of the equation.

4. Balancing Equations 3. Balance by using COEFFICIENTS (numbers) placed in FRONT of the Formulas. The coefficient multiplies everything in the formula.

5. Balancing Equations -- Do Not change the formula. -- Do NOT change subscripts in the chemical formulas of substances to balance equations!!!

6. Balancing Equations 4. Coefficients represent the number of particles or moles. 5. Make sure that the coefficients are the most reduced ratio.

7. Odd-Even Balancing When you end up with an odd number of an element on one side and an even number on the other, solve it by multiplying the things you balanced so far by 2. This problem always occurs with alkanes (C n H 2n+2 ) with even numbered carbons.

8. Balancing Combustion Rxns Start with the carbons Then do the hydrogen Finally, balance the oxygen Remember it by C, H, O

9. Polyatomic Ions in balancing If the P.A.I. stays the same on both sides of the equation, consider the PAI as a unit (one thing), when counting atoms.

10. Practice Problems Write balanced equations for each of the following: 1. Magnesium metal and water react to form magnesium hydroxide and hydrogen gas. 2. When ethane burns it combines with oxygen to form carbon dioxide and water.

11. Practice Problems Balance each of the following equations