Balancing Equations Balancing, Writing, and Naming Equations

Balancing Equations

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

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

Balancing Equations Hydrogen and oxygen are diatomic elements. Their subscripts cannot be changed. The subscripts on water cannot be changed. Hydrogen + oxygen water Hydrogen + oxygen water H 2 + O 2 H 2 O H 2 + O 2 H 2 O

Balancing Equation Count the atoms on each side. Reactant side: 2 atoms H and 2 atoms O Product side: 2 atoms H and 1 atom O H 2 + O 2 H 2 O H 2 + O 2 H 2 O

Balancing Equations H 2 + O 2 H 2 O H 2 + O 2 H 2 O If the subscripts cannot be altered, how can the atoms be made equal? If the subscripts cannot be altered, how can the atoms be made equal? Adjust the number of molecules by changing the coefficients. Adjust the number of molecules by changing the coefficients.

Balancing Equations 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! H 2 + O 2 2H 2 O H 2 + O 2 2H 2 O

Balancing Equations 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! 2H 2 + O 2 2H 2 O 2H 2 + O 2 2H 2 O

Balancing Equations Count atoms. Reactants: 2 atoms N and 2 atoms H Products: 1 atom N and 3 atoms of NH 3 N 2 + H 2 NH 3 N 2 + H 2 NH 3 Nitrogen + hydrogen ammonia Nitrogen + hydrogen ammonia

Balancing Equations Nothing is balanced. Nothing is balanced. Balance the nitrogen first by placing a coefficient of 2 in front of the NH 3. Balance the nitrogen first by placing a coefficient of 2 in front of the NH 3. N 2 + H 2 2NH 3 N 2 + H 2 2NH 3

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

Balancing Equations Count atoms. Reactants: Ca – 3 atoms, P – 2 atoms, O – 8 atoms; H – atoms, S – 1 atom, O – 4 atoms Ca 3 (PO 4 ) 2 + H 2 SO 4 CaSO 4 + H 3 PO 4 Ca 3 (PO 4 ) 2 + H 2 SO 4 CaSO 4 + H 3 PO 4

Balancing Equations Side note on Ca 3 (PO 4 ) 2 Side note on Ca 3 (PO 4 ) 2 The subscript after the phosphate indicates two phosphate groups. The subscript after the phosphate indicates two phosphate groups. This means two PO 4 3- groups with two P and eight O atoms. This means two PO 4 3- groups with two P and eight O atoms.

Balancing Equations Ca 3 (PO 4 ) 2 + H 2 SO 4 CaSO 4 + H 3 PO 4 Ca 3 (PO 4 ) 2 + H 2 SO 4 CaSO 4 + H 3 PO 4 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 Ca 3 (PO 4 ) 2 + H 2 SO 4 CaSO 4 + H 3 PO 4

Balancing Equations Ca 3 (PO 4 ) 2 + H 2 SO 4 CaSO 4 + H 3 PO 4 Ca 3 (PO 4 ) 2 + H 2 SO 4 CaSO 4 + H 3 PO 4 Reactants: Ca 2+ – 3, PO , H + – 2, SO Products: Ca , SO , H + - 3, PO

Balancing Equations Balance the metal first by placing a coefficient of 3 in front of CaSO 4. Balance the metal first by placing a coefficient of 3 in front of CaSO 4. Products: Ca – 3 atoms, SO groups Products: Ca – 3 atoms, SO groups Ca 3 (PO 4 ) 2 + H 2 SO 4 3CaSO 4 + H 3 PO 4

Balancing Equations Three sulfur atoms are needed on the reactant side so place a coefficient of 3 in front of H 2 SO 4. Three sulfur atoms are needed on the reactant side so place a coefficient of 3 in front of H 2 SO 4. 3H 2 SO 4 gives 6 H + and 3 SO H 2 SO 4 gives 6 H + and 3 SO Phosphorus is not balanced. Phosphorus is not balanced. Ca 3 (PO 4 ) 2 + 3H 2 SO 4 3CaSO 4 + H 3 PO 4

Balancing Equations A coefficient of 2 placed in front of H 3 PO 4 which balances phosphorus. Next check hydrogen and oxygen. A coefficient of 2 placed in front of H 3 PO 4 which balances phosphorus. Next check hydrogen and oxygen. Hey, they balanced automatically! Hey, they balanced automatically! Ca 3 (PO 4 ) 2 + 3H 2 SO 4 3CaSO 4 + 2H 3 PO 4

Balancing Equations Remember the order? MNHOL! Cu + H 2 SO 4 Cu + H 2 SO 4 CuSO 4 + H 2 O + SO 2 CuSO 4 + H 2 O + SO 2

Balancing Equations Sulfur is not balanced. Sulfur is not balanced. Place a two in front of sulfuric acid. Place a two in front of sulfuric acid. Cu + 2H 2 SO 4 CuSO 4 + H 2 O + SO 2

Balancing Equations Hydrogen needs to be balanced so place a 2 in front of the H 2 O. Hydrogen needs to be balanced so place a 2 in front of the H 2 O. Count the number of atoms. Count the number of atoms. Cu + 2H 2 SO 4 CuSO 4 + 2H 2 O + SO 2

Balancing Equations It’s balanced! It’s balanced! Cu + 2H 2 SO 4 CuSO 4 + 2H 2 O + SO 2

Balancing Equations Balancing hints: Balancing hints: Balance the metals first. Balance the metals first. Balance the non-metals other than hydrogen and oxygen next. Balance the non-metals other than hydrogen and oxygen next. Then balance the hydrogen and oxygen Then balance the hydrogen and oxygen Balance “loners” last Balance “loners” last

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

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

Writing and Naming Write each formula independently. Write each formula independently. Ignore the rest of the equation. Ignore the rest of the equation. Balance the equation after writing the formulas. Balance the equation after writing the formulas. Ni + HCl NiCl 2 + H 2 Ni + HCl NiCl 2 + H 2 Ni + 2HCl NiCl 2 + H 2 Ni + 2HCl NiCl 2 + H 2

Writing and Naming Remember the diatomic elements: H 2, N 2, O 2, F 2, Cl 2, Br 2, and I 2. Remember the diatomic elements: H 2, N 2, O 2, F 2, Cl 2, Br 2, and I 2.

Writing and Naming Balance the formula equation. Write the word equation. Cu + H 2 SO 4 Cu + H 2 SO 4 CuSO 4 + H 2 O + SO 2 CuSO 4 + H 2 O + SO 2

Writing and Naming Cu + 2H 2 SO 4 Cu + 2H 2 SO 4 CuSO 4 + 2H 2 O + SO 2 CuSO 4 + 2H 2 O + SO 2 Write the names: Cu by itself is just copper. Copper(I) or copper(II) would be incorrect. H 2 SO 4 should be named as an acid. Sulfuric acid

Writing and Naming CuSO 4 has a SO 4 2- group so Cu must be 2+. Some metals must have Roman Numerals. Copper(II) sulfate CuSO 4 has a SO 4 2- group so Cu must be 2+. Some metals must have Roman Numerals. Copper(II) sulfate H 2 O is known as water. H 2 O is known as water. SO 2 is a nonmetal compound. Its name is either sulfur dioxide or sulfur(IV) oxide. SO 2 is a nonmetal compound. Its name is either sulfur dioxide or sulfur(IV) oxide.

Writing and Naming Copper + sulfuric acid  Copper(II) sulfate + water + sulfur dioxide Cu + 2H 2 SO 4 Cu + 2H 2 SO 4 CuSO 4 + 2H 2 O + SO 2 CuSO 4 + 2H 2 O + SO 2

Balancing Equations Chapter 7 Chapter 7 Practice! Practice!