Balancing Equations

1. Balancing Equations

2. Law of Conservation of Mass: • In a chemical reaction, matter can be neither created nor destroyed. • In a chemical reaction, the amount of reactants always equals the amount of products.

3. Balancing Equations • In other words….Law of Conservation of Atoms: • The number of atoms of each type of element must be the same on each side of the equation.

4. Photosynthesis

5. Balancing Equation Hydrogen oxygen water H2 + O2 H2O Is this a balanced equation? To find out…… Step 1: Count the atoms on Reactant side. Step 2: Count the atoms on the Product side • Reactant side: 2 atoms H and 2 atoms O • Product side: 2 atoms H and 1 atom O Not Balanced!!!

6. Balancing Equations H2 + O2 H2O Step 3: Determine which elements are unequal. What can we do to make the products match the reactants? The subscripts cannot be changed. (changing subscripts would result in a new substance)

7. Balancing Equations • H2 + O2 H2O • If the subscripts cannot be altered, how can the atoms be made equal? Step 4: Adjust the number of molecules by changing the coefficients.

8. Balancing Equations H2 + O22H2O • Reactants: 2 atoms of H and 2 atoms of O • Products: 4 atoms of H and 2 atoms of O • O is balanced, but H is no longer balanced! What can we do?!!!!

9. Balancing Equations 2H2 + O22H2O Add a coefficient!!! • Reactant side: 4 atoms of H and 2 atoms of O • Product side: 4 atoms of H and 2 atoms of O It’s Balanced!

10. Balancing Equations 2H2 + O22H2O • Step 5: Double check your work when you are finished.

11. Let’s Practice…. N2 + H2 NH3 Nitrogen + hydrogen ammonia • Count atoms. • Reactants: Products: • N = N= • H= H= Nothing is balanced!!!!

12. Balancing Equations N2 + H22NH3 • Balance the nitrogen first by placing a coefficient of 2 in front of the NH3. Hydrogen is still not balanced. What coefficient should be add to balance the hydrogen?

13. Balancing Equations N2 + 3H22NH3 • Try a 3 in front of H2. • Reactant side: 2 atoms N, 6 atoms H • Product side: 2 atoms N, 6 atoms H The equations is balanced!!!!!

14. Balancing Equations • This method of balancing equations is the inspection method. • The method is trial and error. • Let’s Practice.

15. Practice: ____K3PO4+____HCl ____KCl ____ H3PO4 Balance the formula equation. • Step 1 – Count the atoms • Reactants – K ___, P ___, O ___, H ___, Cl ___ • Products - K ___, P ___, O ___, H ___, Cl ___ Which type of atom is unbalanced?

16. Potassium needs to be balanced!!! • place a 3 in front of the KCl. • Count the number of atoms. ____K3PO4+____HCl  3KCl ____ H3PO4 Reactants – K ___, P ___, O ___, H ___, Cl ___ Products - K ___, P ___, O ___, H ___, Cl ___ Is this equation now balanced? Now we need to fix Chlorine……

17. ____K3PO4+ 3HCl 3KCl ____ H3PO4 Place a 3 in front of HCl Count the number of atoms Reactants – K ___, P ___, O ___, H ___, Cl ___ Products - K ___, P ___, O ___, H ___, Cl ___ Now is the equations balanced? YES!!

18. Practice: ____C3H8 + ____O2 ____CO2 +____ H2O Count the atoms: Reactants: C ___, H ____, O ___ Products: C ___, H ____, O ___ Let’s start with carbon

19. ____C3H8 + ____O23 CO2 +____ H2O Place a 3 in front of CO2 Count the atoms: Reactants: C ___, H ____, O ___ Products: C ___, H ____, O ___ Now let’s fix the hydrogen? What should we try?

20. ____C3H8 + ____O23 CO2 + 4 H2O Place a 4 in front of H2O Count the atoms: Reactants: C ___, H ____, O ___ Products: C ___, H ____, O ___ Now for the oxygen's… what should we try?

21. ____C3H8 + 5 O23 CO2 + 4 H2O Place a 5 in front of the O2 Count the atoms: Reactants: C ___, H ____, O ___ Products: C ___, H ____, O ___ Now are we balanced??

22. Are you up for a challenge?!!! __Ca3(PO4)2+__H2SO4 __CaSO4+__H3PO4 Try this one! • Count atoms. • Reactants: Ca – __ atoms, P – ___ atoms, O – ___ atoms; H – ___atoms, S – ___ atom • Products: Ca – __ atoms, P – ___ atoms, O – ___ atoms; H – ___atoms, S – ___ atom Where should be start?