Chemical Formulas Chapter 20 and 21
Products and Reactants Symbols Reactant (s) Product (s) A (s) solid + B (g) gas C (l) liquid + P ( aq) aqueous dissolved in water delta, means change or difference, (usually requires heating for the reaction to work) light means requires light, sometimes ultraviolet sometimes visible Catalyst a substance which speeds up a reaction without being consumed
Balancing Chemical Formulas H 2 g + O 2g 2H 2 O g Law of Conservation of matter says you must have all matter accounted for after a chemical reaction, so you must have all the parts in the product as you did in the reactants Reactants = 2Hs and 2Os total Products = 4Hs and 2Os, can’t be, doesn't have the same amount of Hs. You can add more of the substance, but you can’t change the substance (can’t change small numbers). So add another molecule of water
Reactants Product H 2 + O 2 2H 2 O Hs Os Hs Os Multiply H 2 x 2 (2 x 2 = 4) Means it is balanced
Reactants Products CH 4 g + O 2 g CO 2 g + H 2 Og C HOCHO Multiply H 2 0 x 2 on the product side Multiply 0 2 x 2 on the reactant side Balanced!
Reactants Products N 2 + 3H 2 NH 3 NHNH 2613 Multiply product x Balanced!
NH 3 + O 2 NO + H 2 O NHONHO Hint –make odd numbers even first (Multiply NH 3 x 2 in the reactant) 2NH 3 +O 2 NO + H 2 O (Multiply H 2 O in product x 3) 2NH 3 + O 2 NO + 3H 2 O (Multiply NO x2 in the product) 2NH 3 + O2 2NO + 3 H 2 O (Multiply O 2 x 2 ½ in the reactant) NH ½ O 2 2NO + 3 H 2 O Have to get rid of the fraction, so multiply everything x NH 3 + 5O 2 4NO + 6H 2 O DONE!
Al 2 (SO 4 ) 3 + Ca(NO 3 ) 2 Al(NO 3 ) 3 + CaSo 4 Can’t break apart parenthesis. Polyatomic and stays in tack. Balance as a unit AlSO 4 CaNO 3 AlSO 4 CaNO Multiply AL(NO 3 ) 3 x 2 in product Multiply Ca(NO 3 ) 2 x 3 in reactant Multiply CaSO 4 x 3 in the product Balanced So, Al 2 (SO 4 ) 3 + 3Ca(NO 3 ) 2 2AL(NO 3 ) 3 + 3CaSO 4
Types of Reactions Combination A + B = AB two or more reactants = 1 product Decomposition AB = A + B one reactant = 1 or more products Single replacement A + BC = B + AC metal + ionic compound = a new metal and a new ionic compound Double replacement AB + CD = CB + AD two ionic compounds = two different ionic compounds
Exothermic reactions Reactants release heat during the reaction Less heat in product Very spontaneous Product + heat energy You would feel the heat given off from the reaction
Endothermic Reaction Absorbs heat during a reaction Keep pumping in heat to keep the reaction going More heat contained inside the products you would feel a cooler sensation because heat is being absorbed by the reactants
Combustion Reactions Ch 6 + 2O 2 CO 2 + 2H 2 O Carbon compound + O 2(g) CO 2(g) + H 2 O (g) Exothermic reaction Releases light and heat