Classifying Chemical Reactions Unit 4, Section 2

Learning Objectives Classify chemical reactions.

Classifying Chemical Reactions There are six types of chemical reactions. – Synthesis – Combustion – Decomposition – Single replacement – Double replacement – Acid-base neutralization Reactions can be classified into more than one category.

Synthesis Reaction A synthesis reaction is a chemical reaction in which two or more substances (A and B) react to produce a single product (AB). In general: A + B  AB Example: CaO (s) + H 2 O (l)  Ca(OH) 2 (s)

Decomposition Reaction A decomposition reaction is one in which a single compound breaks down into two or more elements or new compounds. In general: AB  A + B Example: 2 H 2 O  2H 2 + O 2

Single Replacement Reaction A single-replacement reaction is a reaction in which the atoms of one element replace the atoms of another element in a compound. In general: A + BC → B + AC Example: Cu(s) + 2AgNO 3 (aq)  Ag(s) + Cu(NO 3 ) 2 (aq)

Double Replacement Reaction A double-replacement reaction is a chemical reaction that involves the exchange of ions between two compound. In general: AB + CD → AD + CB Example: Ca(OH) 2 (aq) + 2HCl(aq)  CaCl 2 (aq) + 2H 2 O(l)

Combustion Reaction A combustion reaction is a reaction in which oxygen combines with a substance and releases energy in the form of heat and light. When hydrocarbons (compounds with C and H) are combusted, they react with O 2 to form CO 2 and H 2 O.

Combustion Reaction General reaction: C x H y + O 2 ---> CO 2 + H 2 O Example: CH 4 (g) + 2O 2 (g)  CO 2 (g) + 2H 2 O(g)

Acid-Base Neutralization Reactions An acid-base reaction is a special kind of double displacement reaction that takes place when an acid and base react with each other. The H + ion in the acid reacts with the OH - ion in the base, causing the formation of water. Generally, the product of this reaction is some ionic salt and water: – HA + BOH ---> H 2 O + BA One example of an acid-base reaction is the reaction of hydrobromic acid (HBr) with sodium hydroxide: – HBr + NaOH ---> NaBr + H 2 O

Summary Classifying chemical reactions makes them easier to understand, remember, and recognize. There are six types of chemical reactions: synthesis, combustion, decomposition, single replacement, double replacement and acid- base.

Example Problems Classify the following reactions. 1. 2KNO 3  2KNO 2 + O 2 2.HCl + NaOH  H 2 O + NaCl 3.Zn + 2AgNO 3  Zn(NO 3 ) 2 + 2Ag 4.Ni(NO 3 ) 2 + 2NaOH  Ni(OH) 2 + 2NaNO 3 5.3Mg + N 2  Mg 3 N 2

Practice Problems Classify the following reactions. 1. CH 4 + 2O 2  CO 2 + 2H 2 O 2.N 2 + 3H 2  2NH 3 3.Ni + Cu(NO 3 ) 2  Cu + Ni(NO 3 ) 2 4.CuCO 3  CuO + O 2 5.Ca(OH) 2 + 2HNO 3  Ca(NO 3 ) 2 + 2H 2 O