Chemistry Unit 2

Synthesis Reactions

• Synthesis Reactions are a reaction where two or more reactants combine to form a new product

• Three types of synthesis reactions

  • Two elements form an Ionic Compound

  • Two Elements form a Covalent Compound

  • Two Compounds form a New Compound

• Differences from grade 10

  • You need to list states of matter for products/reactants

    • GENERAL RULES (90% of time): Ionic cmpds -> solid (S/D) or aqueous (SD/DD; diatomic -> Gases mostly (BR is liquid, I is solid); Metals -> solids; nonpolar -> gases; water -> liquid; Acids/Bases -> aqueous

  • You must predict the products 

  • You must balance all equations

  • You may be asked to determine type of reaction

  • You may be asked to name compounds in equation

• Two elements form an Ionic Compound

  • Univalent Metals - when a univalent metal reacts with a non-metal, one ionic compound is formed

    • 2Na_(s) + Cl_2(g) -> 2NaCl_(s)

  • Multivalent Metals - If a metal has more than one ion charge, it is very difficult to predict the product of Synthesis Reaction

    • For multivalent metals you need to indicate all possible products

    • 2Cu_(s) + O_2(g) -> 2CuO_(s) 

    • 4Cu_(s) + O_2(g) -> 2Cu₂O_(s)

• Two elements form a covalent compound NOT ON A TEST

  • When two non-metals react, a covalent compound is formed

  • Since covalent compounds can combine in many different ratios the product must be determined experimentally

    • C_(s) + O_2(g) -> CO_2(g)

    • 2C_(s) + O_2(g) -> 2CO_(g)

    • S_(s) + O_2(g) -> SO_2(g)

  • You can give any answer on a test, won't be on a test

• Two Compounds form a new compound

  • Non metal oxide reacts with water (often producing an acids)

    • CO_2(g) + H₂O_(l) -> H₂CO_3(aq)

    • On a test we are given -ate acids

  • Metal oxide reacts with water (often produces a base)

    • Na₂O_(s) + H₂O_(l) -> 2NaOH_(aq)

Decomposition Reactions

• A reaction where a compound breaks down into two or more products

• Four types of decomposition reactions

  • Binary compound decomposes into elements

  • A metal nitrate decomposes into metal nitrite and oxygen gas

  • A metal carbonate decomposes into metal oxide and carbon dioxide

  • A metal hydroxide decomposes into metal oxide and water

• Binary compound decomposes into elements

  • Heat can be used to decompose a compound (things added on top of arrow/needed for reaction isn't destroyed in reaction - heat isn’t destroyed)

    • Delta (∆) means Heat is added and is placed above or below an arrow

    • 2HgO_(s) -> (∆) 2Hg_(l) + O_2(g)

  • Electricity can be used to decompose a compound (electrolysis)

    • Word electricity is placed above or below an arrow

    • 2H₂O_(l) -> (Electricity) 2H_2(g) + O_2(g)

• A metal nitrate decomposes into a metal nitrite and oxygen gas

  • 2NaNO_3(s) -> 2NaNO_2(s) + O_2(g)

• A metal (or hydrogen) carbonate decomposes into a metal oxide and carbon dioxide

  • CaCO_3(s) -> CaO_(s) + CO_2(g)

  • H₂CO_3(aq) -> H₂O_(l) + CO_2(g)

• A metal hydroxide decomposes into a metal oxide and water

Ca(OH)_2(s) -> (∆) CaO_(s) + H₂O_(l)