A chemical equation describes what happens in a chemical reaction. The equation identifies the reactants (starting materials) and products (resulting substance), the formulas of the participants, the phases of the participants (solid, liquid, gas), and the amount of each substance. Balancing a chemical equation refers to establishing the mathematical relationship between the quantity of reactants and products. The quantities are expressed as grams or moles.
3 Essential steps:
1) Write the unbalanced equation.
· Chemical formulas of reactants are listed on the left-hand side of the equation.
· Products are listed on the right-hand side of the equation.
2) Balance the equation.
· Apply the Law of Conservation of Mass to get the same number of atoms of every element on each side of the equation.
· Once one element is balanced, proceed to balance another, and another, until all elements are balanced.
· Balance chemical formulas by placing coefficients in front of them. Do not add subscripts, because this will change the
formulas.
3) Indicate the states of matter of the reactants and products.
· Use (g) for gaseous substances.
· Use (s) for solids.
· Use (l) for liquids.
· Use (aq) for species in solution in water.
Ex: Balance the equation:
SnO2 + H2 → Sn + H2O
Look at the equation and see which elements are not balanced. There are two oxygen atoms on the left-hand side of the equation and only one on the right-hand side. Correct this by putting a coefficient of 2 in front of water.
SnO2 + H2 → Sn + 2 H2O
This puts the hydrogen atoms out of balance. Now there are two hydrogen atoms on the left and four hydrogen atoms on the right. To get four hydrogen atoms on the right, add a coefficient of 2 for the hydrogen gas. Remember, coefficients are multipliers, so if we write 2 H2O it denotes 2x2=4 hydrogen atoms and 2x1=2 oxygen atoms.
SnO2 + 2 H2 → Sn + 2 H2O
The equation is now balanced. Be sure to double-check your math!
Remember to Indicate the physical states of the reactants and products.
SnO2(s) + 2 H2(g) → Sn(s) + 2 H2O(g)
3 Essential steps:
1) Write the unbalanced equation.
· Chemical formulas of reactants are listed on the left-hand side of the equation.
· Products are listed on the right-hand side of the equation.
2) Balance the equation.
· Apply the Law of Conservation of Mass to get the same number of atoms of every element on each side of the equation.
· Once one element is balanced, proceed to balance another, and another, until all elements are balanced.
· Balance chemical formulas by placing coefficients in front of them. Do not add subscripts, because this will change the
formulas.
3) Indicate the states of matter of the reactants and products.
· Use (g) for gaseous substances.
· Use (s) for solids.
· Use (l) for liquids.
· Use (aq) for species in solution in water.
Ex: Balance the equation:
SnO2 + H2 → Sn + H2O
Look at the equation and see which elements are not balanced. There are two oxygen atoms on the left-hand side of the equation and only one on the right-hand side. Correct this by putting a coefficient of 2 in front of water.
SnO2 + H2 → Sn + 2 H2O
This puts the hydrogen atoms out of balance. Now there are two hydrogen atoms on the left and four hydrogen atoms on the right. To get four hydrogen atoms on the right, add a coefficient of 2 for the hydrogen gas. Remember, coefficients are multipliers, so if we write 2 H2O it denotes 2x2=4 hydrogen atoms and 2x1=2 oxygen atoms.
SnO2 + 2 H2 → Sn + 2 H2O
The equation is now balanced. Be sure to double-check your math!
Remember to Indicate the physical states of the reactants and products.
SnO2(s) + 2 H2(g) → Sn(s) + 2 H2O(g)