Chemical Reactions

• Synthesis reactions involve the combination of two or more substances to form a new compound.
• Single Displacement Reactions involve an element and a compound as reactants.
• In a Single Displacement Reaction, one element takes the place of another element in the compound.
• The general formula for a Single Displacement Reaction is: A(s) + BX(aq) → AX(aq) + B(s).
• The periodic table organizes elements into chemical families.
• Elements in the same family will behave similarly in a chemical reaction.
• We use subscripts to show the states of our compounds and atoms, such as (s) for solid state, (l) for liquid state, (g) for exists in a gas, and (aq) for aqueous (dissolved in a substance).
• A chemical change results when the elements or compounds present at the start of a reaction are rearranged into NEW elements or compounds.
• To displace a substance in a compound, an element must be more reactive than the substance in the compound.
• Clues that a chemical change has occurred: A new colour appears, heat or light is given off, bubbles of gas are formed, a solid material (precipitate) forms in a liquid, the change is difficult to reverse.
• There are 4 main types of chemical reactions: Synthesis reactions, Decomposition reactions, Single displacement reactions, Double displacement reactions.
• The Activity Series is used to determine whether an element is capable of displacing another element.
• Synthesis reactions, also called “combination reactions”, involve two or more reactants combining to produce a new product.
• An element is able to displace any element that is below it on the Activity Series.
• Reactants in synthesis reactions are often elements that combine to make a compound.
• The general formula for synthesis reactions is: X + Y → XY.
• Examples of synthesis reactions include: 2H2 + O2 → 2H2O, N2 + 3H2 → 2NH3, CO2 + H2O → H2CO3.
• Decomposition reactions involve a large molecule being broken down into two or more simpler molecules or elements, serving as the opposite of synthesis reactions.
• The general formula for decomposition reactions is: XY → X + Y.
• Examples of Single Displacement Reactions include Na(s) + H2O(l) → NaOH(aq) + H2(g), Mg(s) + HCl(aq) → MgCl2(aq) + H2(g), AgNO3(aq) + Cu(s) → Cu(NO3)2(aq) + Ag(s), and Mg(s) + KNO3(aq) → N.R (no reaction).
• Examples of decomposition reactions include: H2CO3 → CO2 + H2O, NaCl → Na + Cl, NH4NO3 → N2O + 2H2O.
• Check Your Understanding: Complete worksheets in notes package.
• Cs2S(aq) + NaOH(aq) → AgNO3(aq) + K3PO4(aq)
• In a double displacement reaction, both reactants are compounds and elements in different compounds displace each other.
• In a double displacement reaction, it is the metal cations which exchange places.
• Combustion is the burning of hydrocarbons in the presence of oxygen.
• AB + CD → AD + CB
• Soluble compounds will stay in an aqueous state, while low solubility compounds will precipitate.
• To determine the states of a compound, use the Solubility Table.
• Mg(s) + Cu(NO3)2(aq) → Al(s) + Fe2O3(s) → Zn(s) + HCl
• Ba(OH)2 + Na2SO4 → BaSO4 + NaOH
• Combustion is an exothermic reaction, which releases heat.
• Endothermic Reaction absorbs heat.
• NaOH + HCl → NaCl + H2O
• A precipitate is formed in a double displacement reaction, which is a solid within a liquid.
• Pb(NO3)2 + KI → PbI2 + KNO3
• Double Displacement Reactions
• NaOH(aq) + HCl(aq) → copper(II) bromide + aluminum chloride → aluminum iodide + mercury(II) chloride
• Na(s) + H2O(l) → Al2O3(aq) + Cu(s)
• Chemical reactions occur when a substance is changed into one or more new substances.