1. Chemical Formulas Chapter 20 and 21

2. 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

3. 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

4. Reactants Product H 2 + O 2 2H 2 O Hs Os Hs Os 2 2 4 2 Multiply H 2 x 2 (2 x 2 = 4) 4 24 2 Means it is balanced

5. Reactants Products CH 4 g + O 2 g CO 2 g + H 2 Og C HOCHO 1 42123 Multiply H 2 0 x 2 on the product side 1 42144 Multiply 0 2 x 2 on the reactant side 1 44144 Balanced!

6. Reactants Products N 2 + 3H 2 NH 3 NHNH 2613 Multiply product x 2 2626 Balanced!

7. NH 3 + O 2 NO + H 2 O NHONHO 132122 Hint –make odd numbers even first (Multiply NH 3 x 2 in the reactant) 2NH 3 +O 2 NO + H 2 O 262122 (Multiply H 2 O in product x 3) 2NH 3 + O 2 NO + 3H 2 O 262164 (Multiply NO x2 in the product) 2NH 3 + O2 2NO + 3 H 2 O 262265 (Multiply O 2 x 2 ½ in the reactant) NH 3 + 2 ½ O 2 2NO + 3 H 2 O 265265 Have to get rid of the fraction, so multiply everything x 2 4121041210 2NH 3 + 5O 2 4NO + 6H 2 O DONE!

8. 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 3 23121113 Multiply AL(NO 3 ) 3 x 2 in product 23122116 Multiply Ca(NO 3 ) 2 x 3 in reactant 23362116 Multiply CaSO 4 x 3 in the product 23362336 Balanced So, Al 2 (SO 4 ) 3 + 3Ca(NO 3 ) 2 2AL(NO 3 ) 3 + 3CaSO 4

9. 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

10. 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

11. 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

12. 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