Chapter 8

chemical change – a change in which the original substance(s) become something different with completely different properties indicated by: production of heat, light or electricity formation of a precipitate or a gas possible color change new substance(s), products, have different properties than original substance(s), reactants

chemical equation – a shorthand method of showing what is happening in a chemical Rx similar to a recipe shows what needs to be mixed and what will be made shows how much needs to be mixed and how much will be made shows the phases of the reactants and products

steps to balance a chemical equation 1.start with a word equation propane(C 3 H 8 ) gas burns in the presence of oxygen in the air to form carbon dioxide gas and water vapor 2.create a skeletal equation convert chemical names to chemical symbols C 3 H 8 (g) + O(g)  CO 2 (g) + H 2 O(g)

3.create formula equation check each formula molecules –> from name salts –> oxidation = reduction diatomic elements C 3 H 8 (g) + O (g)  CO 2 (g) + H 2 O(g) once all formulas are correct, NEVER CHANGE OR ADD SUBSCRIPTS!!!!!!! #1 mistake = incorrect formulas 2

4.balance by inspection count atoms/ions on reactant side count atoms/ions on product side FOLLOW LAW OF CONSERVATION OF MASS – what you start with you must end with!!!! C 3 H 8 (g) + O 2 (g)  CO 2 (g) + H 2 O(g) 3 C as a reactant, add a coefficient of 3 in front of C as a product C 3 H 8 (g) + O 2 (g)  CO 2 (g) + H 2 O(g) 3

C 3 H 8 (g) + O 2 (g)  3CO 2 (g) + H 2 O(g) 8 H as reactant, add a 4 as a coefficient in front of H on product side C 3 H 8 (g) + O 2 (g)  3CO 2 (g) + H 2 O(g) C and H are balanced, count O as reactant and O as product 2 O as reactant, 10 as product 4

C 3 H 8 (g) + O 2 (g)  3CO 2 (g) + 4H 2 O(g) add a coefficient of 5 to the reactant O 2 C 3 H 8 (g) + O 2 (g)  3CO 2 (g) + 4H 2 O(g) 5.recheck all atoms/ions start with first reactant 5

a sulfuric acid(H 2 SO 4 ) solution is added to an aqueous solution of sodium hydroxide which forms an aqueous solution of sodium sulfate and water solid potassium chlorate when mixed with a catalyst of manganese dioxide will decompose in to solid potassium chloride and oxygen gas

a solid piece of copper is added to an aqueous solution of silver nitrate which creates solid silver and a copper(II) nitrate solution an aqueous solution of barium nitrate is added to an aqueous solution of aluminum sulfate to produce an aqueous solution of aluminum nitrate and a precipitate of barium sulfate

Types of chemical Rx 1.synthesis Rx simple reactant + simple reactant  single product A + X  AX example

2.decomposition Rx single reactant  two or more products AX  A + X ABX  AB + X types of decomp Rx example

3.single displacement Rx element + compound  different element + different compound AX + B  BX + A example

4.double displacement Rx compound + compound  different compound + different compound one must be: a solid precipitate, or a gas, or water. AX + BY  AY + BX(s),(g),(l) example

5.combustion Rx hydrocarbon + oxygen  carbon dioxide + water three things needed for combustion 1. fuel(hydrocarbon) 2. oxygen 3. NRG source to ignite products of complete hydrocarbon combustion are always 1. carbon dioxide gas 2. water vapor example

 ionic equation all aqueous substances break apart in to ions NaCl(aq)  Na + (aq) + Cl - (aq) NaCl(aq) + AgNO 3 (aq)  NaNO 3 (aq) + AgCl(s) Na + (aq) + Cl - (aq) + Ag + (aq) + NO 3 - (aq)  Na + (aq) + NO 3 - (aq) + AgCl(s)

 net ionic equation list only ions reacting and what they make deduct/eliminate the spectator ions  spectator ions – ions that remain the same on both reactant and product side Na + (aq) + Cl - (aq) + Ag + (aq) + NO 3 - (aq)  Na + (aq) + NO 3 - (aq) + AgCl(s) Cl - (aq) + Ag + (aq)  AgCl(s)