Understanding Chemical Equations and Balancing
Chemical Equation
Definition: A chemical equation is a symbolic representation of a chemical reaction using chemical formulas.
Components:
Reactant (SM): The starting material, or substance undergoing change in a chemical reaction.
Product (P): The substance that results from the reaction.
Common States of Matter for SM and P:
(g): Gas
(l): Liquid
(s): Solid
(aq): Aqueous solution (a solution in water)
Symbols Used in Equations:
: Indicates gas evolution during the course of the reaction.
¯: Indicates precipitation of solid from solution.
Catalyst: A substance that speeds up the reaction without undergoing any overall change itself during the reaction.
Reaction Conditions:
Specific: Conditions like temperature, pressure, solvent, and reaction time.
General:
D: Heat
hn: Light
Electrical current: Represented as a symbol in the equation.
Coefficients and Balancing
Coefficient Definition: A coefficient is a number placed before a substance's formula in a chemical equation.
Purpose: It indicates the relative mole amount of each reactant and product involved.
Balancing Equations:
A balanced equation is one where the number of all atoms on both sides of the equation is equal for each element.
Preferred Coefficients: Use the smallest possible whole numbers.
Balancing Methods:
Inspection (Trial-and-Error): Start with atoms that are represented in only one substance on each side, if possible.
Half-Reactions: This method works particularly well for complex redox (reduction-oxidation) reactions.
Examples of Balancing:
Example 1:
Example 2:
Example 3:
Example 4: