Balancing Chemical Reactions

Steps to Success in Balancing Chemical equations Figure out whose a reactant and whose a product Write the formulas for the reactants on the left side of the arrow (if more than one, separate them with a “+”) Write the formulas for the products on the right side of the arrow (if more than one, separate them with a “+”) List all the atoms in the products and the reactants Use coefficients in front of formulas to make the numbers of atoms in the reactants and products equal Quiz yourself Check your answers

Example 1: Magnesium reacts with hydrochloric acid to form magnesium chloride and hydrogen gas 1. Figure out whose a reactant and whose a product Reactant Product Magnesium magnesium chloride Hydrochloric acid hydrogen 2. Write the formulas for the reactants on the left side of the arrow (if more than one, separate them with a “+”) Mg + HCl  3. Write the formulas for the products on the right side of the arrow (if more than one, separate them with a “+”) Mg + HCl  MgCl2 + H2(g)* *hydrogen is diatomic

Example 1 (cont): Magnesium reacts with hydrochloric acid to form magnesium chloride and hydrogen gas 4. List all the atoms in the products and the reactants Mg + HCl MgCl2 + H2(g)*  Mg 1 H 1 Cl 1 Mg 1 H 2 Cl 2 5. Use coefficients* in front of formulas to make the numbers of atoms in the reactants and products equal Mg + 2 HCl MgCl2 + H2(g)*  Mg 1 H 2 1 Cl 2 1 Mg 1 H 2 Cl 2 * The coefficient multiples all the atoms in the molecule that its in front of

Example 2: Barium chloride reacts with sodium phosphate to form sodium chloride and barium phosphate 1. Figure out whose a reactant and whose a product Reactant Product Barium chloride sodium chloride Sodium phosphate barium phosphate 2. Write the formulas for the reactants on the left side of the arrow (if more than one, separate them with a “+”) BaCl2 + Na3PO4  3. Write the formulas for the products on the right side of the arrow (if more than one, separate them with a “+”) NaCl + Ba3(PO4)2  BaCl2 + Na3PO4

Example 2 (cont): Barium chloride reacts with sodium phosphate to form sodium chloride and barium phosphate 4. List all the atoms in the products and the reactants NaCl + Ba3(PO4)2  BaCl2 + Na3PO4 Ba 1 Cl 2 Na 3 P 1 O 4 Ba 3 Cl 1 Na 1 P 2 O 8 5. Use coefficients* in front of formulas to make the numbers of atoms in the reactants and products equal 6 NaCl + Ba3(PO4)2  3 BaCl2 + 2 Na3PO4 Ba 3 1 Cl 6 2 Na 6 3 P 2 1 O 8 4 Ba 3 Cl 6 1 Na 6 1 P 2 O 8 * The coefficient multiples all the atoms in the molecule that its in front of

Example 3: When heated, ammonium carbonate breaks down into gaseous ammonia, carbon dioxide and water vapor 1. Figure out whose a reactant and whose a product Reactant Product Ammonium carbonate ammonia carbon dioxide water 2. Write the formulas for the reactants on the left side of the arrow (if more than one, separate them with a “+”) (NH4)2CO3  3. Write the formulas for the products on the right side of the arrow (if more than one, separate them with a “+”) (NH4)2CO3  NH3(g) + CO2(g) + H2O(g)

Example 3 (cont): When heated, ammonium carbonate breaks down into gaseous ammonia, carbon dioxide and water vapor 4. List all the atoms in the products and the reactants (NH4)2CO3  NH3(g) + CO2(g) + H2O(g) N 2 H 8 C 1 O 3 N 1 H 5 C 1 O 3 5. Use coefficients* in front of formulas to make the numbers of atoms in the reactants and products equal (NH4)2CO3  2 NH3(g) + CO2(g) + H2O(g) N 2 H 8 C 1 O 3 N 2 1 H 8 5 C 1 O 3 * The coefficient multiples all the atoms in the molecule that its in front of

Example 4: In plants, carbon dioxide and water combine to form glucose and oxygen 1. Figure out whose a reactant and whose a product Reactant Product Carbon dioxide glucose water oxygen 2. Write the formulas for the reactants on the left side of the arrow (if more than one, separate them with a “+”) CO2(g) + H2O  3. Write the formulas for the products on the right side of the arrow (if more than one, separate them with a “+”) CO2(g) + H2O  C6H12O6 + O2(g)

Example 4 (cont): In plants, carbon dioxide and water combine to form glucose and oxygen 4. List all the atoms in the products and the reactants CO2(g) + H2O  C6H12O6 + O2(g) C 1 H 2 O 3 C 6 H 12 O 8 5. Use coefficients* in front of formulas to make the numbers of atoms in the reactants and products equal 6 CO2(g) + 6 H2O  C6H12O6 + 6 O2(g) C 6 1 H 12 2 O 18 3 C 6 H 12 O 16 8 * The coefficient multiples all the atoms in the molecule that its in front of

Your turn Balance the following equations: Zinc and lead (II) nitrate react to form zinc (II) nitrate and lead. Aluminum bromide and chlorine gas react to form aluminum chloride and bromine gas A solution of silver (I) nitrate reacts with solid copper to form copper (II) nitrate and solid silver. Calcium hydroxide and phosphoric acid react to form calcium phosphate and water. Potassium metal reacts with chlorine gas to form potassium chloride. Iron (III) oxide reacts with hydrogen gas to form solid iron and water.

the Answers Zinc and lead (II) nitrate react to form zinc nitrate and lead. Zn + Pb(NO3)2  Zn(NO3)2 + Pb already balanced Aluminum bromide and chlorine gas react to form aluminum chloride and bromine gas 2 AlBr3 + 3 Cl2 (g)  2 AlCl3 + 3 Br2 (g) A solution of silver (I) nitrate reacts with solid copper to form copper (II) nitrate and solid silver. 2 Ag(NO3) + Cu  Cu(NO3)2 + 2Ag Calcium hydroxide and phosphoric acid react to form calcium phosphate and water. 3 Ca(OH)2 + 2 H3PO4  Ca3 (PO4)2 + 6 H2O Potassium metal reacts with chlorine gas to form potassium chloride. 2 K + Cl2 (g)  2 KCl Iron (III) oxide reacts with hydrogen gas to form solid iron and water. Fe2O3 + 3 H2 (g)  2 Fe + 3 H2O