Chemical Reactions and Equations

Chemical Reaction A process in which one or more substances are converted into new substances with different physical and chemical properties. Involves 2 types of substances: –Reactant = substance that enters into a chemical reaction –Product = substance produced by a chemical reaction

Chemical Equation A condensed statement that uses chemical formulas or names and identifies the reactants and products in a chemical reaction 2 different forms: –Word equation uses names of reactants and products –Formula equation uses formulas of reactants and products

Reaction: Hydrogen gas combines with Oxygen gas to form water vapor.

Word Equation: Reactants  PProducts Hydrogen + Oxygen  Water vapor

Formula Equation: Reactants PProducts 2H 2 (g) + O 2 (g)  2H 2 O(g)

2H 2 (g) + O 2 (g)  2H 2 O(g) yields

2H 2 (g) + O 2 (g)  2H 2 O(g) Physical States: (s) = solid(g) = gas (l) = liquid(aq) = aqueous

2H 2 (g) + O 2 (g)  2H 2 O(g) Subscripts = number of atoms of each element in the molecule

2H 2 (g) + O 2 (g)  2H 2 O(g) Coefficients = the number of molecules or moles of molecules; act as multipliers

Let’s practice one together When lithium hydroxide pellets are added to a solution of sulfuric acid, lithium sulfate and water are formed.

What are the reactants? 1. lithium hydroxide 2. sulfuric acid What are the products? 1. lithium sulfate 2. water

Word Equation: Lithium hydroxide + sulfuric acid  lithium sulfate + water

FORMULAS Lithium hydroxide LiOH Sulfuric acid H 2 SO 4 Lithium sulfate Li 2 SO 4 Water H2OH2O

Write the formula equation and add in the states of matter for each reactant and product LiOH (s) + H 2 SO 4 (aq)  Li 2 SO 4 (aq) + H 2 O (l)

Looks good, but there’s a problem… LiOH (s) + H 2 SO 4 (aq)  Li 2 SO 4 (aq) + H 2 O (l)

The Law of Conservation of Matter states that matter is neither created nor destroyed in any process. This means that mass is not created or destroyed either. For mass to remain constant before and after a chemical reaction, the number of atoms of each element must be the same before and after a chemical reaction.

How do we get the number of atoms of each element to be the same on each side of the equation? BALANCE!!

LiOH (s) + H 2 SO 4 (aq)  Li 2 SO 4 (aq) + H 2 O (l) Reactants 1 Li atom 5 O atoms 3 H atoms 1 S atom Products 2 Li atoms 5 O atoms 2 H atoms 1 S atom 2 2 Li atoms 6 O atoms 4 H atoms 2 6 O atoms 4 H atoms