Balancing, Writing, and Naming Equations Balancing Equations Balancing, Writing, and Naming Equations

Balancing Equations

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.

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.

Hydrogen + oxygen water 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.

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

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.

Balancing Equations H2 + O2 2H2O 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!

Balancing Equations 2H2 + O2 2H2O 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!

Nitrogen + hydrogen ammonia 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

Balancing Equations N2 + H2 2NH3 Nothing is balanced. Balance the nitrogen first by placing a coefficient of 2 in front of the NH3. N2 + H2 2NH3

Balancing Equations N2 + 3H2 2NH3 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 + 3H2 2NH3

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

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.

Balancing Equations Ca3(PO4)2 + H2SO4 CaSO4 + H3PO4 Count atoms in the product. Ca atoms – 1, S atom – 1, O atoms – 4; H atoms – 3, P atom – 1, O atoms - 4

Balancing Equations Ca3(PO4)2 + H2SO4 CaSO4 + H3PO4 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

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

Balancing Equations Ca3(PO4)2 + H2SO4 3CaSO4 + H3PO4 Balance the metal first by placing a coefficient of 3 in front of CaSO4. Products: Ca – 3 atoms, SO42- - 3 groups Ca3(PO4)2 + H2SO4 3CaSO4 + H3PO4

Balancing Equations Ca3(PO4)2 + 3H2SO4 3CaSO4 + H3PO4 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 + 3H2SO4 3CaSO4 + H3PO4

Balancing Equations Ca3(PO4)2 + 3H2SO4 3CaSO4 + 2H3PO4 A coefficient of 2 placed in front of H3PO4 which balances both hydrogen and phosphate. Ca3(PO4)2 + 3H2SO4 3CaSO4 + 2H3PO4

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

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

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

Balancing Equations Cu + 2H2SO4 CuSO4 + 2H2O + SO2 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

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