The Chemical Reaction Equation

What it’s all about How much of what to react with something else to make something new. Conservation of mass is the overarching principle. Just as many of each element after as before.

+

Used to separate the reactants from each other and the products from each other Symbolizes the addition of another compound or element

→

Symbolizes “yields” or “forms” Used to separate the reactant side of the equation from the product side

↔

Used to communicate a chemical reaction is reversible i.e. it can go both ways

X (s )

The (s) written as a subscript means the element or compound is in the solid form.

X(l)X(l)

The ( l ) written as a subscript means the element or compound is in the liquid form.

X (g)

The (g) written as a subscript means the element or compound is in the gaseous form.

X (aq)

The (aq) stands for aqueous which means the element or compound is dissolved in water.

→

The triangle over the arrow means heat must be added to the reaction for it to go.

The formula above the arrow represents the presence of a catalyst.

Definition: A catalyst is a substance which speeds up a reaction without being consumed.

∆

The triangle represent heat and/or energy as either a reactant or product

4H 2

The number in front of a formula represents how many moles are required for the reaction to go to completion »completion means all of the reactants are consumed

Reactants are always written to the left of the arrow. Products are always written to the right of the arrow.

Sample reaction: What is ALL of the information the reaction tells us?

2HCl (aq) + Mg (s) → MgCl 2(aq) + H 2(g)