Ch. 4: Compounds and Stoichiometry Flashcards
Compounds
Substances composed of 2 or more elements in a fixed proportion
Molecular Weight
Mass in (amu) of the constituent atoms in a compound as indicated by the molecular formula
Molar mass
Mass of one mole (Avogadro’s number) of a compound; usually measured in grams per mole
Gram equivalent weight
Measure of the mass of asubstance that can donate one equivalent of the species of interest
Normality
Ratio of equivalents per liter; it is related to molarity by multiplying the molarity by the number of equivalents present per mole of compound
Equivalents
Moles of the species of interest; equivalents are most often seen in acid-base chemistry (hydrogen ions or hydroxide ions) and oxidation-reudction reactions (moles of electrons or other ions)
Law of constant composition
States that any pure sample of a compound will contain the same elements in the same mass ratio
Empirical Formula
Smallest whole-number ratio of the elements in a compound
Molecular Formula
Either the same as or a multiple of the empirical formula; it gives the exact number of atoms of each element in a compound
Percent Composition by Mass
Determine the mass of the individual element and divide by the molar mass of the compound
Combination Reaction
Occur when 2 or more reactants combine to form one product
Decomposition Reaction
Occur when one reactant is chemically broken down into 2 or more products
Combustion reaction
Occurs when a fuel and an oxidant (typically oxygen) react, forming the products water and carbon dioxide (if the fuel is a hydrocarbon)
Displacement Reactions
Occur when one or more atoms or ions of one compound are replaced w one or more atoms or ions of another compound
Single Displacement Reactions
Occur when an ion of one compound is replaced with another element
Double Displacement Reactions
Occur when elements from 2 diff compounds trade places w each other to form 2 new compounds
Neutralization Reactions
Are those in which an acid reacts with a base to form a salt (and, usually, water)
Balancing a Chemical Equation
Chemical equations must be balanced to perform stoichiometric calculations
- Balance the least common atoms
- Balance the more common atoms (usually hydrogen and oxygen)
- Balance the charge, if necessary
Limiting Reagent
The reactant that will be consumed first in a chemical rxn
Excess Reagent
Reactants that are not limiting
Theoretical Yield
Amt of product generated if all of the limiting reactant is consumed w no side reactions
Actual Yield
Typically lower than theoretical yield
Percent yield
Calculated by dividing actual yield by theoretical yield and converting to a percentage
Roman Numerals
Used for nonrepresentative elements to denote ionic charge
-ous
Can be used to indicate lesser charge (cations)
-ic
Can be used to indicate greater charge (cations)
-ide
All monoatomic anions end in -ide
Oxyanion suffix to indicate oxidation
Indicate how oxidized the central atom is
- Less oxygen are given suffix -ite
- More oxygen are give -ate
Oxyanion series w more than 2 members
Fewest oxygens given prefix hypo-, the most oxygens is given prefix per-
Polyatomic ions containing hydrogen
polyatomic ions containing hydrogen denote the number of hydrogens using hydrogen or bi to denote one, or dihydrogen to denote 2
Ionic Charges
Predictable by group number and type of element (metal or nonmetal) for representative elements, but are generally unpredictable for nonrepresentative elements
- Metals form positively charged cations based on group number
- Nonmetals form negatively charged anions based on the number of electrons needed to achieve an octet
Electrolytes
Contain equivalents of ions from molecules that dissociate in solution. The strength of an electrolyte depends on its degree of dissociation or solvation
