Balancing Equations

what do you multiply

subscript x coefficient

why do we balance equations

to show the reaction followed the law of conservation mass

the goal is to have the same number of atoms of each element on each side of the reaction that way we have the same mass on each side.

rule that cannot be broken

never change the subscripts in a formal that changes what the chemical is

it's okay to change coefficients but it s not okay to arrange subscripts

three ways to balance a chemical reaction

1. by inspection (just looking at it)

2. by trial and error

3. by the algebraic method

no matter the method you use always use atom inventory to check the amount of atoms on each side of the equation.

What are the 5 types of chemical reactions?

1. Synthesis

2. Decomposition

3. Combustion

4. Single Replacement

5. Double replacement

Define SYNTHESIS reaction

 A compound is made from simpler materials

Combination reaction is another term for synthesis

Example: C(s) + O₂ →CO₂ (g) 

The general equation for a synthesis reaction: A + B → AB

Define DECOMPOSITION reaction

A compound is broken down into simpler compounds, or down to the elements that make it up.

Example: H₂O (l) →H₂ (g) + O₂ (g)

The general equation for decomposition reaction: AB → A+B

Define COMBUSTION reaction

A compound containing carbon and hydrogen (and sometimes oxygen) combines with oxygen to produce carbon dioxide and water.

Example: CH₄ (g) + O₂ (g) →CO₂ (g) + H₂O (g)

What is combustion a fancy word for? Burning.

General equation for combustion reaction: C_xH_y(O₂) →CO₂ + H₂O

Example of combustion reaction with oxygen: C₂H₅OH (I) + O₂ (g) →CO₂ (g) + H₂O

Define SINGLE REPLACEMENT reaction

One element that starts out by itself replaces another element in a compound, kicking it out.

Example: Fe (s) + CuCl₂ (aq) → Cu (s) + FeCl₂ (aq)

The general equation for a single replacement reaction: A + BC →B +AC

Note: Also sometimes called a single displacement reaction.

Define DOUBLE REPLACEMENT reaction

The positive and negative ions in two compound switch places

Example: BaCl₂ (aq) + Na₂SO₄ (aq) →BaSO₄(s) + NaCl (aq)

The general equation for double replacement reaction: AB +CD →AD +BC

Note: * Also sometimes called a double displacement reaction.

          * All the compounds are IONIC, so they can break down into positive and negative ions.

          * The positive and negative ions just switch places.