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Balancing Chemical Reactions
Steps to Success in Balancing Chemical equations
1. Figure out whose a reactant and whose a product
2. Write the formulas for the reactants on the left side of the arrow (if more than one, separate them with a “+”)
3. Write the formulas for the products on the right side of the arrow (if more than one, separate them with a “+”)
4. List all the atoms in the products and the reactants
5. Use coefficients in front of formulas to make the numbers of atoms in the reactants and products equal
6. Quiz yourself
7. 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 ProductMagnesium magnesium chlorideHydrochloric 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 1H 1Cl 1
Mg 1H 2Cl 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 1H 2 1Cl 2 1
Mg 1H 2Cl 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 ProductBarium chloride sodium chlorideSodium 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
4. List all the atoms in the products and the reactants
Ba 1Cl 2Na 3P 1O 4
Ba 3Cl 1Na 1P 2O 8
5. Use coefficients* in front of formulas to make the numbers of atoms in the reactants and products equal
* The coefficient multiples all the atoms in the molecule that its in front of
Example 2 (cont): Barium chloride reacts with sodium phosphate to form sodium chloride and barium phosphate
NaCl + Ba3(PO4)2 BaCl2 + Na3PO4
6 NaCl + Ba3(PO4)2 3 BaCl2 + 2 Na3PO4
Ba 3 1Cl 6 2Na 6 3P 2 1O 8 4
Ba 3Cl 6 1Na 6 1 P 2O 8
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 ProductAmmonium carbonate ammonia
carbon dioxidewater
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)
4. List all the atoms in the products and the reactants
N 2H 8C 1O 3
5. Use coefficients* in front of formulas to make the numbers of atoms in the reactants and products equal
* The coefficient multiples all the atoms in the molecule that its in front of
Example 3 (cont): When heated, ammonium carbonate breaks down into gaseous ammonia, carbon dioxide and water vapor
(NH4)2CO3 NH3(g) + CO2(g) + H2O(g)
(NH4)2CO3 2 NH3(g) + CO2(g) + H2O(g)
N 1H 5C 1O 3
N 2H 8C 1O 3
N 2 1H 8 5C 1O 3
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 ProductCarbon dioxide glucosewater 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)
4. List all the atoms in the products and the reactants
C 1H 2O 3
5. Use coefficients* in front of formulas to make the numbers of atoms in the reactants and products equal
* The coefficient multiples all the atoms in the molecule that its in front of
Example 4 (cont): In plants, carbon dioxide and water combine to form glucose and oxygen
C 6H 12O 8
CO2(g) + H2O C6H12O6 + O2(g)
6 CO2(g) + 6 H2O C6H12O6 + 6 O2(g)
C 6 1H 12 2O 18 3
C 6H 12O 16 8
Your turnBalance the following equations:
1 Zinc and lead (II) nitrate react to form zinc (II) nitrate and lead.
2 Aluminum bromide and chlorine gas react to form aluminum chloride and bromine gas
3 A solution of silver (I) nitrate reacts with solid copper to form copper (II) nitrate and solid silver.
4 Calcium hydroxide and phosphoric acid react to form calcium phosphate and water.
5 Potassium metal reacts with chlorine gas to form potassium chloride.
6 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
