Chemistry Chapter 10Chemistry Chapter 10

Chemical Reactions – The Basics

Chemical Reactions – The Basics

A chemical reaction is what occurs when elements combine into compounds, separate into elements, or rearrange from one compound into another.

Chemical Reactions – The Basics

A chemical reaction is what occurs when elements combine into compounds, separate into elements, or rearrange from one compound into another.

Chemical reactions are represented by chemical equations.

Chemical Reactions – The Basics

A chemical reaction is what occurs when elements combine into compounds, separate into elements, or rearrange from one compound into another.

Chemical reactions are represented by chemical equations. The reactants (starting chemicals) are shown the left and products (ending chemicals) are shown on the right.

Reactants → Products

Reactants → Products

The arrow separates the reactants and the products.

Reactants → Products

The arrow separates the reactants and the products.

If there are more than 1 reactant/product, then a “+” sign is used in-between, to mean “and”.

Reactants → Products

The arrow separates the reactants and the products.

If there are more than 1 reactant/product, then a “+” sign is used in-between, to mean “and”.

Reactant 1 + Reactant 2 → Product 1 + Product 2

Other Symbols

Symbol Meaning

(s) Solid chemical

(l) Liquid chemical

(g) Gas chemical

(aq) Chemical is dissolved in water (aquated)

Steps for Writing a Chemical Equation

Steps for Writing a Chemical Equation

1. If given a word equation, turn it into a skeleton equation.

Steps for Writing a Chemical Equation

1. If given a word equation, turn it into a skeleton equation.

Example:

Solid iron and gaseous chlorine react to produce solid iron(III) chloride

becomes…

Steps for Writing a Chemical Equation

1. If given a word equation, turn it into a skeleton equation.

Example:

Solid iron and gaseous chlorine react to produce solid iron(III) chloride

becomes…

Fe(s) + Cl2(g) → FeCl3(s)

Steps for Writing a Chemical Equation

2. If given (or you’ve made) a skeleton equation, then balance the equation.

Steps for Writing a Chemical Equation

2. If given (or you’ve made) a skeleton equation, then balance the equation. The arrow in a chemical equation means the amounts of the chemicals on the left must equal the amounts of the chemicals on the right.

Steps for Writing a Chemical Equation

2. If given (or you’ve made) a skeleton equation, then balance the equation. The arrow in a chemical equation means the amounts of the chemicals on the left must equal the amounts of the chemicals on the right.

Example: Fe(s) + Cl2(g) → FeCl3(s)

Steps for Writing a Chemical Equation

2. If given (or you’ve made) a skeleton equation, then balance the equation. The arrow in a chemical equation means the amounts of the chemicals on the left must equal the amounts of the chemicals on the right.

Example: Fe(s) + Cl2(g) → FeCl3(s)

On the left: 1 iron On the right: 1 iron

2 chlorines 3 chlorines

Balancing a Chemical Equation

Balancing a Chemical Equation

Basically a guess and check process.

Balancing a Chemical Equation

Basically a guess and check process.

The only thing you can change is the coefficient!

Balancing a Chemical Equation

Basically a guess and check process.

The only thing you can change is the coefficient!

Coefficients are the numbers in front of a compound and get multiplied to everything in that compound.

Fe(s) + Cl2(g) → FeCl3(s)

Step 1: Add more Cl2

Fe(s) + 2Cl2(g) → FeCl3(s)

Fe(s) + Cl2(g) → FeCl3(s)

Step 1: Add more Cl2

Fe(s) + 2Cl2(g) → FeCl3(s)This gives: 1 iron 1 iron

4 chlorines 3 chlorines

It’s not equal, so we’re not done yet…

Fe(s) + 2Cl2(g) → FeCl3(s)

Step 2: Add more FeCl3

Fe(s) + 2Cl2(g) → 2FeCl3(s)

Fe(s) + 2Cl2(g) → FeCl3(s)

Step 2: Add more FeCl3

Fe(s) + 2Cl2(g) → 2FeCl3(s)This gives: 1 iron 2 iron

4 chlorines 6 chlorines

It’s not equal, so we’re not done yet…

Fe(s) + 2Cl2(g) → 2FeCl3(s)

Step 3: Add more Fe and Cl2

2Fe(s) + 3Cl2(g) → 2FeCl3(s)

Fe(s) + 2Cl2(g) → 2FeCl3(s)

Step 3: Add more Fe and Cl2

2Fe(s) + 3Cl2(g) → 2FeCl3(s)This gives: 2 iron 2 iron

6 chlorines 6 chlorines

It’s equal, we’re done! It’s balanced!