Presentation on theme: "AP CHEMISTRY Summer Review Main Topics: - Ch. 1/ sig. figs; conversion problems; density - Ch 2/ counting p +, n o, & e - ; naming & writing formulas -"— Presentation transcript:
AP CHEMISTRY Summer Review Main Topics: - Ch. 1/ sig. figs; conversion problems; density - Ch 2/ counting p +, n o, & e - ; naming & writing formulas - Ch. 3/ balancing eq.; % composition; empirical formulas stoichiometry conversions; limiting reagents; % Yield Other: - Orbital diagrams; Dot notation
AP CHEMISTRY Significant Figures The number of significant figures is the number of digits known with certainty plus one uncertain digit. (Example: g means we are sure the mass is _______ but we are uncertain about the nearest g.) Final calculations are only as significant as the least significant measurement g
AP CHEMISTRY Sig. Fig. Rules 1) Nonzero digits are significant. (Nonzero Rule) Example: 2.45 cm =________ 2) Zeros between sig. figs. are significant. (Straddle Rule) Example: 2.03 cm=_________ 3) Zeros at the end of the number and after a decimal point are significant. (Righty-Righty Rule) Example: cm=_________ 3 s.f 4 s.f 3 s.f
AP CHEMISTRY 4) Zeros at the end of a number before a decimal point are ambiguous…In some cases, a bar will be placed over a zero to eliminate the ambiguity or the number will be written in scientific notation. (Bar Rule) Example: 10,300 grams = _____________ x 10 4 g = _________ 5) If a number is known for certain, it is said to contain an infinite number of sig. figs. (Counting Rule) Example: 60 seconds =1 minute at least 3 s.f. 4 s.f (60 is known to # of s.f.)
AP CHEMISTRY Significant Figures in Calculations Multiplication and Division: - Report to the least number of significant figures Example: cm x 5.2 cm = _______ Addition and Subtraction: - Report to the least number of decimal places Example: 20.4 g – g = _______ 32 cm g
AP CHEMISTRY Density Density= mass/volume -Density can be used as a conversion factor as well! Density mass volume
AP CHEMISTRY Counting p +, n o and e - Protons = Atomic Number Electrons = protons (in a neutral atom) Neutrons = Mass # - protons Mass Number = protons + neutrons Gaining electrons gives an atom a (-) charge. Losing electrons gives an atom a (+) charge.
AP CHEMISTRY Naming Compounds Molecules– Contains only 2 nonmetals; covalent bonding. General Format Prefix (except mono)-name 1 st element prefix-name 2 nd element ending in –ide
Naming Compounds Ionic– Starts with metallic cation (or NH 4 + ); ionic bonding. General Format Cation Name Anion Name You will have to memorize the cation and anion symbols & charges! We will have a quiz over them later!
AP CHEMISTRY Naming Compounds Acids– Starts with H
AP CHEMISTRY Balancing Equations You can only change coefficients! Example: C 3 H 8 + __O 2 __CO 2 + __H 2 O 345
AP CHEMISTRY Percent Composition AW stands for the atomic weight of the atom from the periodic table. FW stands for the formula weight of the compound.
AP CHEMISTRY Empirical Formulas Helpful Rhyme: % to mass, mass to mole, divide by small, times til whole.
AP CHEMISTRY Stoichiometry Conversion Factors 1 mole = 22.4 L (at STP) = 6.02 x particles = FW (grams) These conversions will take up to 3 steps and no more! Always convert to moles of given first!
AP CHEMISTRY Stoichiometry Conversions- (gram to gram)
AP CHEMISTRY Limiting Reagent (or Reactant) The reactant that runs out first limits the amount of product that can be formed. Stoichiometry conversions can be done to determine which substance is the limiting reagent.
AP CHEMISTRY % Yield The amount of product predicted from stoichiometry taking into account limiting reagents is called the theoretical yield. The percent yield relates the actual yield (amount of material recovered in the laboratory) to the theoretical yield: