Lesson · C.2.2

Reactions and equations

How to read, balance, and classify a chemical equation for the HESI A2 Chemistry subtest, with the five reaction types and the factors that speed a reaction up.

ObjectiveC.2.2Read5 minExam weightBonding and Reactions ≈ 24% of Chemistry

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What you will be able to do

Balance a chemical equation using conservation of mass.
Classify a reaction as synthesis, decomposition, combustion, single replacement, or double replacement.
Name the four factors that increase reaction rate and explain why each one works.

What the lesson concludes

A balanced equation has the same number of each atom on both sides, since matter is conserved, not created or destroyed.
The five reaction types are synthesis, decomposition, combustion, single replacement, and double replacement.
Temperature, surface area, concentration, and catalysts all speed up a reaction by increasing how often particles collide with enough energy.
A catalyst lowers the activation energy needed for a reaction and is not consumed by it.
Coefficients in a balanced equation give the mole ratio between reactants and products, the basis for stoichiometry.