Regents Analysis – Moles/Stoichiometry/Solutions
The following are the most frequently (not the only!) asked topics on the regent’s exam from the Math of Chemistry.
Solving percent composition problems.
Calculate empirical formulas and the relation to true (molecular) formulas.
Use of the tables of solubility, F and G.
Using equations to determine relations between moles. (No mass-mass, mass-volume, volume-volume problems)
Relation between density and volume of a gas at STP.
Four types of reactions: synthesis, decomposition, single replacement, double replacement, as well as combustions (be able to identify and predict products and reactants).
All reactions include conservation of mass, energy and charge.
Create and use models to demonstrate balanced equations.
Mole conversions but not particles in a mole (6.02 x 1023)
Parts per million (formula on table T)
You should know these facts about the Moles/Stoichiometry/Solutions Unit.
Moles are used to count atoms and molecules.
Avogodro’s number is 6.02 x 1023
The mass of one mole of any thing is the sum of their atomic weights
Gram atomic mass is the mass in grams of a mole of atoms ex: Sulfur is 32 amu or 32 grams per mole (containing Avogadro’s number of atoms)
Gram formula mass is the sum of the masses of a molecule. Ex H2O = 18 amu or 18 grams per mole
One mole of any gas occupies 22.4 liters at STP
Stoichiometry is a study of the molar proportions
Percent composition is the relative percentages of each element in a formula
Solutions contain two parts solute and solvent
The solute is the lesser quantity, solvent is the greater quantity
“Like dissolve like” (polar dissolves polar, non polar dissolves non polar)
Molarity is a measure of a solutions strength (see table T)
Immiscible means not mixing
Dilute solutions are weak solutions (low amounts of solute vs. solvent)
Solutions are saturated, unsaturated and supersaturated (see table G)
Freezing point depression is the lowering of the freezing point of water
Boiling point elevation is the raising of the boiling point of water.
Reference Tables to know for this section.
Table F: Solubility Guidelines for Aqueous Solutions, Reference Tables page 6 & 7 (see description at bottom of page) Review Pages 3:10, 6:5, 6:6, 7:14.
Table G: Solubility Curves, Reference Tables page 8. Review pages 6:1 – 6:3.
Table T: Important Formulas and Equations. Mole Calculations: 5:20. Percent Error: 12:1-12:2. Percent Composition: 5:19. Concentration: 6:6 – 6:9.
Review Book: Chapter 5 & 6.
Text Book: Chapter 10,11 & 15.
dstreib: Regents Analysis, Moles/Stoichiometry/Solutions