Balancing Equations

1. Balancing Equations Balancing, Writing, and Naming Equations

2. Balancing Equations

3. Balancing Equations • Law of Conservation of Matter: • In a chemical reaction, matter can be neither created nor destroyed. • In a chemical reaction, the amount of reactants equal the amount of products.

4. Balancing Equations • Paraphrase: • Law of Conservation of Atoms: • The number of atoms of each type of element must be the same on each side of the equation.

5. Balancing Equations Hydrogen + oxygen water H2 + O2 H2O • Hydrogen and oxygen are diatomic elements. • Their subscripts cannot be changed. • The subscripts on water cannot be changed.

6. Balancing Equation H2 + O2 H2O • Count the atoms on each side. • Reactant side: 2 atoms H and 2 atoms O • Product side: 2 atoms H and 1 atom O

7. Balancing Equations • H2 + O2 H2O • If the subscripts cannot be altered, how can the atoms be made equal? • 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 • H is no longer balanced!

9. Balancing Equations 2H2 + O22H2O • 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 N2 + H2 NH3 Nitrogen + hydrogen ammonia • Count atoms. • Reactants: 2 atoms N and 2 atoms H • Products: 1 atom N and 3 atoms of NH3

11. Balancing Equations • Nothing is balanced. • Balance the nitrogen first by placing a coefficient of 2 in front of the NH3. N2 + H22NH3

12. Balancing Equations • Hydrogen is not balanced. • Place a 3 in front of H2. • Reactant side: 2 atoms N, 6 atoms H • Product side: 2 atoms N, 6 atoms H N2 + 3H22NH3

13. Balancing Equations Ca3(PO4)2 + H2SO4 CaSO4 + H3PO4 • Count atoms. • Reactants: Ca – 3 atoms, P – 2 atoms, O – 8 atoms; H – atoms, S – 1 atom, O – 4 atoms

14. Balancing Equations • Side note on Ca3(PO4)2 • The subscript after the phosphate indicates two phosphate groups. • This means two PO43- groups with two P and eight O atoms.

15. Balancing Equations • Ca3(PO4)2 + H2SO4CaSO4 + H3PO4 • Count atoms in the product. • Ca atoms – 1, S atom – 1, O atoms – 4; H atoms – 3, P atom – 1, O atoms - 4

16. Balancing Equations • In this equation, the ion groups do not break up. • Instead of counting individual atoms, ion groups may be counted. • Ca3(PO4)2 + H2SO4 CaSO4 + H3PO4

17. Balancing Equations • Ca3(PO4)2 + H2SO4 CaSO4 + H3PO4 • Reactants: Ca2+ – 3, PO43- - 2, H+ – 2, SO42+ - 1 • Products: Ca2+ - 1, SO42- - 1, H+ - 3, PO43- - 1

18. Balancing Equations • Balance the metal first by placing a coefficient of 3 in front of CaSO4. • Products: Ca – 3 atoms, SO42- - 3 groups • Ca3(PO4)2 + H2SO43CaSO4 + H3PO4

19. Balancing Equations • Three sulfate groups are needed on the reactant side so place a coefficient of 3 in front of H2SO4. • 3H2SO4 gives 6 H+ and 3 SO42-. • Neither phosphate nor calcium is balanced. • Ca3(PO4)2 + 3H2SO43CaSO4 + H3PO4

20. Balancing Equations • A coefficient of 2 placed in front of H3PO4 which balances both hydrogen and phosphate. • Ca3(PO4)2 + 3H2SO43CaSO4 + 2H3PO4

21. Balancing Equations Cu + H2SO4 CuSO4 + H2O + SO2 • The sulfate group breaks up. Each atom must be counted individually. Ugh! • Reactants: Cu – 1, H – 2, S – 1, O – 4 • Products: Cu – 1, S – 1, O - 4, H – 2, O – 1, S – 1, O - 2

22. Balancing Equations • Sulfur is not balanced. • Place a two in front of sulfuric acid. • Count atoms: 2 H2SO4 H – 4, S – 2, O - 8 • Cu + 2H2SO4 • CuSO4 + H2O + SO2

23. Balancing Equations • Hydrogen needs to be balanced so place a 2 in front of the H2O. • Count the number of atoms. • Cu + 2H2SO4 • CuSO4 + 2H2O + SO2

24. Balancing Equations • Reactants: Cu – 1, H – 4, S – 2, O – 8 • Products: Cu – 1, S – 1, O – 4, H – 4, O – 2, S – 1, O – 2 = Cu – 1, S – 2, H – 4, O – 8 • It’s balanced! • Cu + 2H2SO4 • CuSO4 + 2H2O + SO2

25. Balancing Equations • Balancing hints: • Balance the metals first. • Balance the ion groups next. • Balance the other atoms. • Save the non ion group oxygen and hydrogen until the end.

26. Balancing Equations • This method of balancing equations is the inspection method. • The method is trial and error. • Practice.

27. Writing and Naming Nickel + hydrochloric acid Nickel(II) chloride + hydrogen • Write the corresponding formula equation and then balance the equation.

28. Writing and Naming • Write each formula independently. • Ignore the rest of the equation. • Balance the equation after writing the formulas. Ni + HCl NiCl2 + H2 Ni + 2HCl NiCl2 + H2

29. Writing and Naming • Remember the diatomic elements: H2, N2, O2, F2, Cl2, Br2, and I2.

30. Writing and Naming Cu + H2SO4 CuSO4 + H2O + SO2 • Balance the formula equation. • Write the word equation.

31. Writing and Naming • Cu + 2H2SO4 • CuSO4 + 2H2O + SO2 • Write the names: • Cu by itself is just copper. Copper(I) or copper(II) would be incorrect. • H2SO4 should be named as an acid. • Sulfuric acid

32. Writing and Naming • CuSO4 has a SO42- group so Cu must be 2+. Some metals must have Roman Numerals. Copper(II) sulfate • H2O is known as water. • SO2 is a nonmetal compound. Its name is either sulfur dioxide or sulfur(IV) oxide.

33. Writing and Naming Cu + 2H2SO4 CuSO4 + 2H2O + SO2 • Copper + sulfuric acid  • Copper(II) sulfate + water + sulfur dioxide

34. Balancing Equations • Practice! • Practice! • Practice!