4.2 Synthesis and Decomposition Reactions Chemical Reactions 4.2 Synthesis and Decomposition Reactions

Last Class Reviewed chemical reactions and chemical equations Reviewed how to balance chemical equations

Learning Goals We are learning to… Identify and predict the products of synthesis and decomposition reactions

Chemical Reactions Most chemical reactions can be grouped into 4 categories Synthesis Decomposition Single displacement Double displacement

Synthesis Reactions Two reactants combine to make a larger/more complex product. General Formula: A + B  AB Example: Synthesis of sodium chloride Na(s) + Cl(g)  NaCl(s)

Example Write the balanced chemical equation for the reaction of magnesium with oxygen Identify the reactants Identify the type of rxn Predict products Skeleton equation Balance

Synthesis Reactions (non-metals) Reactions involving hydrogen Follow a similar pattern as those involving metals. Although covalent, you can use charges to predict products Ex: H2(g) + Cl2(g)  2HCl (g) We can apply the ionic changes of H (+1) and Cl (-1)

Example Write the balanced chemical equation for the reaction of hydrogen with oxygen Identify the reactants Identify the type of rxn Predict products Skeleton equation Balance

Synthesis Reactions (non-metals) Reactions not involving hydrogen Products are difficult to predict Ex: Depending on reaction conditions C(s) + O2(g)  CO2(g) or 2C(s) + O2(g)  2CO(g)

Synthesis Reactions (non-metals) Reactions involving compounds Products may be difficult to predict Ex: water and carbon dioxide react to form carbonic acid H2O(l) + CO2(g)  H2CO3(aq)

Example Water reacts with sulfur trioxide in a synthesis reaction to form sulfuric acid Write the balanced chemical equation, include states.

Decomposition Reactions A reaction in which a larger compound breaks down to form two (or more) simpler products General Formula: AB  A + B Ex: The decomposition of potassium chloride 2KCl(s)  2K(s) + Cl2(g)

Decomposition Reactions Decomposition reactions involving polyatomic ions or molecular compounds can be difficult to predict – do not break apart like binary ionic compounds Ex: potassium chlorate decomposes to produce potassium chloride and oxygen KClO3(s)  KCl(s) + O2(g)

Example calcium carbonate decomposes to produce calcium oxide and carbon dioxide Write the balanced chemical equation, include states.

Homework page 161 # 1-4, 6, 7, 9