2.13 Types of Chemical Reactions

(Sec 9.3 pg 239-247)

• There are 6 kinds of reactions that you need to be familiar with (summarized in Table 1 p.245):

• Synthesis: In general, a synthesis reaction is the combination of 2 substances to form one new compound – ‘two parts become one’.

A + B → AB

• Decomposition: During decomposition, one compound is ‘decomposed’ (broken down) into smaller pieces; the ‘pieces’ may be elements or simpler compounds.

AB → A + B

• Single Replacement: During single replacement, one element reacts with a compound (which contains elements), and one of the elements in the compounds is ‘replaced’.

AB + C →CB + A

• Double Replacement: During double replacement, the cations and anions of two different compounds switch places – essentially, one element from each compound replace each other.

AB + CD → CB + AD

• Acid-Base Neutralization: An acid base reaction involves an acid and a base. When an acid and base (completely) neutralize each other, they produce a salt and water.

H-X + B-OH → BX + H-OH

• Combustion: Combustion, at its most general, can mean the reaction of oxygen gas (O2) with anything.

• However, in this course we’ll be considering the combustion of hydrocarbons – when hydrocarbons react with O2 the products are carbon dioxide, water. This type of reaction also releases energy (e.g. light, heat, etc.)

CxHy + O2→CO2 + H2O

• If you are given the reactants in a chemical reaction, you need to be able to predict the reaction type.

• This will allow you to predict the products, which is very useful in chemistry.

• After determining predicted products, you will need to balance your equation (it will be a ‘skeleton equation’).

• Some tips for making this easier (you might also want to check out the text examples p.245-7):– If the reactant is a single compound, it will break apart

(decomposition)– If you are combining two elements, they can only undergo

synthesis.– If you are combining two ionic compounds, you are dealing

with either double replacement, or an acid-base neutralization. If the reactants are an acid and a base, it is a neutralization reaction. If not, it will be a double replacement.

– If you are combining a hydrocarbon (or anything) with O2, it is a combustion reaction.

– If you are adding a single element to an ionic compound (as your reactants), you are likely dealing with a single replacement reaction.