Balancing Equations

• I can identify the products and reactants in a chemical reaction.• I can state the law of conservation of matter.• I can determine the number of each atom in a compound based on subscripts and coefficients.

•Chemical equations show the reactants and the products of a reaction.• The reactant are on the left side of the equation.• They show which elements or compounds are required for the reaction to occur.

• The products are on the right side of the equation.• The products show which elements or compounds are made during the reaction.• The arrow in a chemical equation means yield or produce.

•According to the law of conservation of matter, matter cannot be created or destroyed.• Therefore, we must balance equation to make sure matter is not created or destroyed.

•Subscripts are the numbers in a formula after an element, down below.• Example: What is the subscript in H2O? 2

•Subscripts cannot be changed when balancing equations.

• Instead, we must add coefficients which are the numbers that go in front of a formula.• Example: What is the coefficient in 5CO2?

• The number of atoms in a formula depends on the coefficients and subscripts.• You multiply the coefficient by the subscripts to determine how many atoms of each element you have.

• Example: How many atoms of each element are in 2C6H12O6?

•Carbon= ___ Hydrogen=___•Oxygen=___

Balancing Act

• I can explain why it is necessary to balance equations.• I can balance chemical equations.• I can distinguish between the

coefficients and subscripts.

Balancing Act

• Atoms are not created or destroyed during a chemical reaction. Scientist know that there must be the same number of atoms on each side of the equation. To balance the chemical equation, you must add coefficients in front of the chemical formulas in the equation. You cannot add or delete subscripts!

Mg + O2 MgO

Mg = Mg =

O = O =

Ca + O2 CaO

Ca = Ca=

O= O=

N2 + H2 NH3

N= N=

H= H=

Cu2O+ C Cu + CO2

Cu = Cu=

O= O=

C= C=

H2O2 H2O + O2

H= H=

O= O=

Balancing Equations

• I can balance equations that contain parenthesis.• I can write and balance word equations.

• The rules of balancing equations apply to molecules in parenthesis as well.• The subscript outside the parenthesis is distributed to all of the atoms inside.

Example

•Al2(SO4)3

•Knowing this, you can now balance any equation.

Word Equations

•Words like and and react with mean a plus sign.•Words like produce or make or yield mean an arrow.• The reactants in an equation are the molecule that go into a reaction.• They are on the left hand side of the equation.

Word Equations

• The products in an equation are the molecules that are made.• They are on the right hand side of the equation.

Example

• Write the balanced chemical equation for the reaction between liquid water and solid calcium metal. The reaction produces calcium hydroxide Ca(OH)2 and hydrogen gas H2.