Chapter 3 from Chem 1303

 6.022 x 10^23 1 mole= 6.022 x 10^23 units
 chemical formula
 A chemical formula shows the ratio by atoms and by moles of elements in the formula
 Molar mass of an element
 atomic mass in grams of 1 mole or 6.022 x 10^23 atoms of an element
 molecular mass
 sum of all atomic masses of elements in a formula “formula weight” and “molecular weight” are often used instead
 Mass spectrometer
 an instrumental technique used to determine atomic mass or molecular mass
 3 types of chemical formulas
 1. empirical formula: shows the simplest ratio of the elements present2. molecular formula: shows the actual number of atoms in one molecule 3. structural formula: shows how the atoms are connected
 Percentage Composition
 mass % of elements in a compound theoretical % composition–from given formula %= (n x molar mass of element)/molar mass of compound x 100% -where n= number of moles of element (from formula)
 chemical reaction
 a process in which a substance (or substances) is changed into one or more new substances
 chemical equation
 uses chemical symbols to show what happens during a chemical reaction
 Stoichiometry
 quantitative study of reactants and products ALWAYS WORK IN MOLES!!!
 Limiting Reactant Calculations
 -one reagent is excess and some is left over– other quantity “limits” how much product can be made-analogous to baking brownies when the mix calls for two eggs and you only have one. Thus you use only half the bag of mix– the limiting reactant is the one that is completely consumed. It determines the maximum amount (yield) of the products-whenever quantities of both reactants are given, the limiting reactant must be determined!
 actual yield
 amount of product actually obtained experimentally
 theoretical yield
 amount of product predicted by balanced equation and limiting reagent
 percentage yield
 percentage yield = (actual yield/theoretical yield) x 100% NOTE: the % yield can never be more than 100%