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2.8 BALANCING CHEMICAL EQUATIONS

2.8 BALANCING CHEMICAL EQUATIONS. HOMEWORK “2.8 Balancing Chemical Equations Worksheet” (this will be handed in tomorrow). In any chemical reaction , we cannot gain or lose any mass or the number of atoms . If the reactants have four atoms in total,

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2.8 BALANCING CHEMICAL EQUATIONS

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  1. 2.8 BALANCING CHEMICAL EQUATIONS

  2. HOMEWORK • “2.8 Balancing Chemical Equations Worksheet” (this will be handed in tomorrow)

  3. In any chemical reaction, • we cannot gain or lose any mass or the number of atoms. • If the reactants have four atoms in total, • then the products must have four atoms in total.

  4. Let’s look at an example: • Make a compound out of Mg and F. Remember how to do this? • Mg 2+ F 1- • MgF2

  5. So an equation for what we just did is the following: • Mg + F  MgF2 • Let’s look at the number of atoms on each side of the equation: • ATOM REACTANTS PRODUCTS • (left side) (right side) Mg 1 1 2 F 1

  6. We call this equation “unbalanced” • because one side of the equation has more atoms than the other side. • All chemical formulas must be “balanced” • or have the same number of atoms on both sides before we can call it a correct chemical equation.

  7. So, let’s balance the equation: • Mg + F  MgF2 • What do I need to do in order to have the same amount of atoms on both sides? Mg F Mg F F +  F

  8. Mg + 2 F  MgF2 • This equation now tells me in order to make MgF2, • I need to combine one atom of Mg with • two atoms of F. • This equation is now balanced • (there are the same amount of atoms on each side).

  9. STEPS FOR BALANCING CHEMICAL EQUATIONS • 1. The chemical formula of a compound of atom CANNOT be changed. Eg: We could not have made MgF2 into MgF! • 2. Count the number of atoms in both the reactants and products. Use a chart to help you. • 3. Balance each formula by the appropriate coefficient • (number before the chemical) to balance the number of atoms for both the reactants and the products. • 4. Balance oxygen and hydrogen last.

  10. Example: Balance the following chemical equation: • Ba3(PO4)2 + CaO  BaO + Ca3(PO4)2 ATOM REACTANTS PRODUCTS Ba P Ca O 3 1 2 2 1 3 9 9 • Which atoms are unbalanced? • Ba and Ca • Let’s balance Barium.

  11. What do we need to do? ATOM REACTANTS PRODUCTS Ba P Ca O 3 1 x3 2 2 1 3 9 9

  12. We need to put a three in front of BaO. • Ba3(PO4)2 + CaO 3BaO + Ca3(PO4)2 ATOM REACTANTS PRODUCTS Ba P Ca O 3 3 2 2 1 3 9 11 Now, are we balanced? No

  13. Let’s balance another atom: Ca. • What do we need to do? ATOM REACTANTS PRODUCTS Ba P Ca O 3 3 2 2 x3 1 3 9 11

  14. We need to put a three in front of CaO. Ba3(PO4)2 + 3 CaO 3 BaO + Ca3(PO4)2 ATOM REACTANTS PRODUCTS Ba P Ca O 3 3 2 2 3 3 11 11

  15. Now, are we balanced? Yes • We have the same amount of atoms on both sides of the equation.

  16. HOMEWORK • “2.8 Balancing Chemical Equations Worksheet” (this will be handed in tomorrow)

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