balancing equations tutorial this tutorial will take you through steps necessary to balance chemical...
TRANSCRIPT
Balancing Equations tutorial
• This tutorial will take you through steps necessary to balance chemical equations.
Law of the Conservation of Mass
• The law of conservation of mass states that the mass of the starting material equals the mass of all products at the end of the reaction.
• In chemical terms, mass is equivalent to the elements involved.
Consequences
• If the Law of conservation of mass was not correct:
• Imagine eating a sandwich---- a chemical reaction that occurs in your mouth----if the law of conservation of mass did not exist, your food could disappear (or increase in size) from time to time.
Steps to solve a balancing equations problem
• Organize your information
• Examine the formulae in the problem
• Check rows and columns to keep track of the problems.
Sample problem
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
Step 1: SetupThe double line is like an equal
sign. __ KCl + __ Fe2O3 => __ K2O + __ FeCl3
Step 2: Initial inventoryList elements (or ions).
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K
Cl
Fe
O
Step 3: Inventory formulas
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K __ x 1 __ x 2
Cl __ x 1 __ x 3
Fe __ x 2 __ x 1
O __ x 3 __ x 1
Step 4: Check set-up
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K __ x 1 __ x 2
Cl __ x 1 __ x 3
Fe __ x 2 __ x 1
O __ x 3 __ x 1
All numbers match the formulas.
Step 5: Filling in the table
• Here are the basic rules and hints:– For each row, the left side of the double line must equal
the right side of the double line.
– For each column, Each underlined number MUST be the same.
– Begin in a row where the numbers are not the same.
– When you fill in row, continue from the numbers that you filled in. DO NOT JUMP AROUND THE TABLE.
Start with row of ClLeast common multiple of 1 and 3 is 3.
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K __ x 1 __ x 2
Cl _3 x 1 1 x 3
Fe __ x 2 __ x 1
O __ x 3 __ x 1
Since we see a 3 underlined in the first column, we can enter a three in the row above
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K _3 x 1 __ x 2
Cl _3 x 1 1 x 3
Fe __ x 2 __ x 1
O __ x 3 __ x 1
We have a problem here. The number that would fit in the Potassium row would be 1.5, but all numbers
must be whole numbers so multiple by 2.
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K _3 x 1 __ x 2
Cl _3 x 1 1 x 3
Fe __ x 2 __ x 1
O __ x 3 __ x 1
We have a problem here. The number that would fit in the Potassium row would be 1.5, but all numbers
must be whole numbers so multiple by 2.
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K _6 x 1 __ x 2
Cl _6 x 1 2 x 3
Fe __ x 2 __ x 1
O __ x 3 __ x 1
Continue on with the potassium row
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K _6 x 1 _3 x 2
Cl _6 x 1 2 x 3
Fe __ x 2 __ x 1
O __ x 3 __ x 1
Now the Potassium oxide column
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K _6 x 1 _3 x 2
Cl _6 x 1 2 x 3
Fe __ x 2 __ x 1
O __ x 3 _3 x 1
Now the oxygen row
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K _6 x 1 _3 x 2
Cl _6 x 1 2 x 3
Fe __ x 2 __ x 1
O _1 x 3 _3 x 1
Now the Iron (III) oxide column
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K _6 x 1 _3 x 2
Cl _6 x 1 2 x 3
Fe _1 x 2 __ x 1
O _1 x 3 _3 x 1
Now the Iron row.
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K _6 x 1 _3 x 2
Cl _6 x 1 2 x 3
Fe _1 x 2 2 x 1
O _1 x 3 _3 x 1
The underlined numbers in the Iron (III) chloride column match. This is a good sign.
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K _6 x 1 _3 x 2
Cl _6 x 1 2 x 3
Fe _1 x 2 2 x 1
O _1 x 3 _3 x 1
Check to see if each row equals out on the left and right sides of the double lines.
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K _6 x 1 _3 x 2
Cl _6 x 1 2 x 3
Fe _1 x 2 2 x 1
O _1 x 3 _3 x 1
Check to see if each underlined number in each column is the same.
__ KCl + __ Fe2O3 => __ K2O + __ FeCl3
K _6 x 1 _3 x 2
Cl _6 x 1 2 x 3
Fe _1 x 2 2 x 1
O _1 x 3 _3 x 1
The numbers all check, so we can fill in the coefficients in the equation.
6 KCl + 1 Fe2O3 => 3 K2O + 2 FeCl3
K _6 x 1 _3 x 2
Cl _6 x 1 2 x 3
Fe _1 x 2 2 x 1
O _1 x 3 _3 x 1
You are done.
The answer is
6 KCl + 1 Fe2O3 => 3 K2O + 2 FeCl3