Stoichiometry of Chemical Reactions

Chemical Equations

Chemical equations represent chemical reactions
Coefficients: indicate the relative numbers of molecules of each kind
Subscripts: indicate composition; changing the subscript changes the identity of the molecule.

Dissolution: the process where a solute dissolves in a solvent to form a solution
Solubility: the maximum concentration of a solute that can dissolve in a solvent at a given temperature
When dissolution occurs, two or more substances disperse (or disappear) into each other to form a homogeneous solution.
Dissociation: when an ionic substance dissolves in water, the solvent pulls the individual ions from the crystal and solvates them.

Molecular equation: shows complete chemical formulas of reactants and products
All water-soluble, ionic compounds exist as ions in solution
To write the net ionic equation, break these compounds up into ions
Ions that appear on both sides of the arrow will cancel out
Ions that cancel out are called spectator ions
Net ionic equation: shows reactants and products actually participating in the reaction

Acids defined by Arrhenius: substances that increase the concentration of H+ when dissolved in water.
Acids defined by J. N. Brønsted and T. M. Lowry: acids as proton donors.
Based defined by Arrhenius: substances that increase the concentration of OH− when dissolved in water.
Bases defined by Brønsted and Lowry: proton acceptors.

Oxidation numbers: bookkeeping device to track loss or gain of electrons in a redox reaction
To determine if an oxidation–reduction reaction has occurred, assign an oxidation number to each element in a neutral compound or charged entity
1. Elements in their elemental form have an oxidation number of 0.
2. The oxidation number of a monatomic ion is the same as its charge.
3. Nonmetals usually have negative oxidation numbers
  a) Oxygen is usually -2 except in peroxides where it is -1
  b) Hydrogen is +1 when bonded to nonmetals and -1 when bonded to metals
  c) Fluorine is -1 in all compounds. Other halogens usually have an oxidation
  number of -1 except in oxyanions where they have a positive oxidation number
4. The sum of the oxidation numbers in a neutral compound is zero; in a polyatomic ion the sum is equal to the charge on the ion.

Theoretical yield: the quantity of product calculated to form when all of the limiting reactant is consumed.
Actual yield: the quantity of product actually obtained (usually less than the theoretical yield).
Percent Yield = (Actual Yield/Theoretical Yield) x 100%

Titration: an analytical technique in which one can calculate the concentration of a solute in a solution.
Titrant: solution in the buret; known in the concentration; can be either acid or base depending on the nature of the analyte
Analyte: solution being analyzed; solution in flask; solution of unknown concentration
Equivalence point: volume of titrant where moles titrant and moles of analyte are exactly equal
End point: the physical indication of the equivalence point; comes after the actual equivalence point