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Chapter 3 from Chem 1303
review for final
14
Chemistry
Undergraduate 1
12/08/2014

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Term
Avogadro's Number
Definition
6.022 x 10^23

1 mole= 6.022 x 10^23 units
Term
chemical formula
Definition
A chemical formula shows the ratio by atoms and by moles of elements in the formula
Term
Molar mass of an element
Definition
atomic mass in grams of 1 mole or 6.022 x 10^23 atoms of an element
Term
molecular mass
Definition
sum of all atomic masses of elements in a formula

"formula weight" and "molecular weight" are often used instead
Term
Mass spectrometer
Definition
an instrumental technique used to determine atomic mass or molecular mass
Term
3 types of chemical formulas
Definition
1. empirical formula: shows the simplest ratio of the elements present
2. molecular formula: shows the actual number of atoms in one molecule
3. structural formula: shows how the atoms are connected
Term
Percentage Composition
Definition
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)
Term
chemical reaction
Definition
a process in which a substance (or substances) is changed into one or more new substances
Term
chemical equation
Definition
uses chemical symbols to show what happens during a chemical reaction
Term
Stoichiometry
Definition
quantitative study of reactants and products

ALWAYS WORK IN MOLES!!!
Term
Limiting Reactant Calculations
Definition
-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!
Term
actual yield
Definition
amount of product actually obtained experimentally
Term
theoretical yield
Definition
amount of product predicted by balanced equation and limiting reagent
Term
percentage yield
Definition
percentage yield = (actual yield/theoretical yield) x 100%

NOTE: the % yield can never be more than 100%
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