Introduction to classifying types of chemical reactions
Why classify chemical reactions? There are so many chemical reactions that occur daily in living things, laboratories, and industry. Classifying the different types of reactions helps keep them organized and easier to understand. Think like a library; so many books, they need to be classified into categories like fiction,non-fiction,biographies,etc. Same thing goes with chemical reactions
Scientists classify reactions into 5 types Synthesis A + B AB CombustionA + O 2 heat + H 2 O + AO 2 DecompositionAB A + B Single-replacementA + BX AX + B Double-replacementAX + BY AY + BX
Synthesis Reactions Two elements combine to produce one new compound. Example synthesis reaction: Iron combines with chlorine gas to produce iron(III) chloride. 2 Fe(s) + 3 Cl 2 (g) 2FeCl 3 (s)
Synthesis reaction continued… Just as 2 elements can combine, 2 compounds can also combine to form one compound. This is also classified as a synthesis reaction. Example: calcium oxide reacts with water to form calcium hydroxide CaO(s) + H 2 O(l) Ca(OH) 2 (s)
Combustion Reactions Oxygen combines with a substance and releases energy in the form of heat and light. Oxygen can combine with many different substances, making combustion reactions a common occurrence. Some combustion reactions are also synthesis reactions; but not all combustion reactions are synthesis reactions.
Combustion reactions continued…. The reaction involving methane gas, CH 4, and oxygen illustrates a combustion reaction in which one substance replaces another in the formation of the products. This is NOT a synthesis reaction. CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O(g)
Decomposition Reactions Opposite of synthesis reactions A single compound breaks down into two or more elements or new compounds. These reactions require an energy source, such as heat, light, or electricity. Example: ammonium nitrate breaks down into dinitrogen monoxide and water when the reactant is heated to high temperature NH4NO3(s) N2O(g) + 2H2O(g)