Chemical Formulas

Chapter 20 and 21

Products and Reactants• 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 the reaction requires heatinglight –means requires light, sometimes ultraviolet

sometimes visibleCatalyst –a substance which speeds up a reaction

without being consumed

Balancing Chemical Formulas

H2 g + O2g 2H2Og • Law of Conservation of matter says you must have all

matter accounted for after a chemical reaction, so you must have all of the parts in the product that you began with in the reactants

• Reactants = 2Hs and 2Os total• Products = 4Hs and 2Os, can’t be, doesn't have the

same amount of Hs in the product and reactant.• You can add more of the substance, but you can’t

change the substance (can’t change small numbers) but you can change the numbers out in front (coefficients). So, add another molecule of water

Reactants Products

• H2 + O2 2H2OHs Os Hs Os

2 2 4 2 So Multiply H2 x 2 (2 x 2 = 4)

Then you would have 4 2 4 2

Means it is balanced

• CH4g + O2g CO2g + H2Og • C H O C H O• 1 4 2 1 2 3• Multiply H20 x 2 on the product side• 1 4 2 1 4 4• Multiply 02 x 2 on the reactant side• 1 4 4 1 4 4• Balanced!• So, CH4 + 2O2 CO2 +2H20

• N2 + 3H2 NH3

• N H N H• 2 6 1 3• Multiply product x 2• 2 6 2 6• Balanced!

NH3 + O2 NO + H2O

N H O N H O• 1 3 2 1 2 2• Hint –make odd numbers even• (Multiply NH3 x2 in the reactant) 2NH3 +O2 NO + H2O• 2 6 2 1 2 2• (Multiply H2O in product x 3) 2NH3 + O2 NO + 3H2O• 2 6 2 1 6 4• (Multiply NO x2 in the product) 2NH3 + O2 2NO + 3 H2O• 2 6 2 2 6 5• (Multiply O2 x 2 ½ in the reactant) NH3 + 2 ½ O2 2NO + 3 H2O • 2 6 5 2 6 5• Have to get rid of the fraction, so multiply everything x 2• 4 12 10 4 12 10• 2NH3 + 5O2 4NO + 6H2O DONE!

Al2(SO4)3 + Ca(NO3)2 Al(NO3)3 + CaSo4

• Can’t break apart parenthesis. Polyatomic and stays in tack. Balance as a unit (none like this on test)

• Al SO4 Ca NO3 Al SO4 Ca NO3

• 2 3 1 2 1 1 1 3• Multiply AL(NO3)3 x 2 in product• 2 3 1 2 2 1 1 6• Multiply Ca(NO3)2 x 3 in reactant• 2 3 3 6 2 1 1 6• Multiply CaSO4 x 3 in the product• 2 3 3 6 2 3 3 6• Balanced• So, Al2(SO4)3 + 3Ca(NO3)2 2AL(NO3)3 + 3CaSO4

Types of reactionsExothermic 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

Types of reactionsEndothermic 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

Types of reactionsCombustion Reactions

• Ch6 + 2O2 CO2 + 2H2O

• Carbon compound + O2(g) CO2(g) + H2O(g)

• Exothermic reaction• Releases light and heat

Other types of Reactionsnone of this on test

• 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