1. FORMULAS, EQUATIONS AND MOLES
Chemical Equation
Stoichiometry
Chemical Formula

2. CHEMICAL REACTION
Rearrangement of the atoms present in the reacting substances to give new chemical combinations present in the product substances.

3. CHEMICAL EQUATION Shorthand symbolic notation for a chemical reaction
Qualitative aspect
identity of reactants [R] and products [P]; use study of nomenclature to write equations
Identify the state of matter for each [R] and [P]
identify reaction type

4. CHEMICAL EQUATION (2) Quantitative aspect
how much reactant is consumed and how much product is formed
coefficients must be consistent with the Law of Conservation of Mass; atoms are neither created nor destroyed in a chemical reaction.
i.e. chemical equation must be balanced

5. FORMULA UNIT
Qualitative description of elements which comprise the chemical unit
Describes an atom, ion, molecular or ionic compound: Mg, NH4+, C12H22O11, KCl
Quantitative description of relative numbers of atoms of each element

6. FORMULA or MOLECULAR MASS
Sum of atomic masses of constituent atoms in the formula unit.
Average mass of one formula unit of substance (atom, molecule, ion, formula unit) in amu
Average mass of one mole of formula units of substance in grams

7. MOLE The number of C-12 atoms in exactly 12 grams of pure C-12
6.022E+23 items
Avogadro’s Number, N
A mole of an element has a mass equal to its average atomic mass

8. CONVERSIONS Grams to Moles Divide by Molar Mass*
* = Atomic, Molar or Formula Mass
Moles to Grams x by Molar Mass
Grams to amu x by N
amu to Grams Divide by N
Moles to #Units** x by N
#Units to Moles Divide by N
** = Atoms, Molecules, Formula Units

9. STOICHIOMETRY
Quantitative relationships based on a BALANCED chemical reaction.
Relationships between R(eactant)1 and R2 or R1 and P(roduct)2 or P1 and P2

10. C(s) + 2H2(g)  CH4(g)
One atom of solid carbon reacts with two molecules of gaseous hydrogen to produce one molecule of gaseous methane.
One mole of solid carbon reacts with two moles of hydrogen gas to produce one mole of methane gas.
12.0 g of C reacts with 4.0 g of H2 to produce 16.0 g of CH4. Note conservation of mass.

11. STOICHIOMETRIC COEFFICIENTS
We will use mole interpretation for stoich. coefficients
represent number of moles of each R and P
Provide quantitative (i.e. mole) relationships between R and P.
Can be used to determine amount of mass of each R and P

12. MOLE RATIOS Use as conversion factors from R1 to R2, P2 to R1, etc
Depend on a balanced chemical equation

13. C(s) + 2H2(g)  CH4(g) 1 mol 2 mol  1 mol 12.0 g 2.0 g  16.0 g
How many g of carbon are needed to react with 10 g of hydrogen? How much CH4is formed
g-H2  mol-H2  mol-C  g-C
[10.0g H2 /2.0g H2/mol]*[1 molC/2 mol H2] * [12.0g C/mol] = 30 g C
[10.0g H2 /2.0g H2/mol]*[1 molCH4/2 mol H2] * [16.0g CH4/mol] = 40 g CH4
Is mass conserved?

14. REACTION YIELD
In the previous example, say that only 32.0 g of CH4 were produced due to side reactions and waste.
We define the percent or reaction yield as [actual yield/theoretical yield]*100
This gives % yield = [32/40] * 100 = 80%

15. LIMITING REACTANT
Find the actual mole ratios of the reactant. Compare this ratio to the stoichiometric mole ratio to determine the limiting reactant or reagent (LR); the other is the excess reactant (xs)
Use the LR to solve the stoichiometric problem to find the amount of product formed.
Calculate the amount of xs left over.

16. SOLUTIONS Most chem rxns occur in a solution
Solution - homogenous mixture
Solvent - compound in solution present in greatest amount
Solute - other compounds present in soln
Concentration
Measure of quantity of solute in solvent
Molarity = M = #moles solute per l liter soln

17. SOLUTIONS(2) # moles = molarity * volume(L) = M * V
Dilution Mc * Vc = Md * Vd where c = concentrated and d = dilute
Stoichiometric calculations for reactions taking place in aqueous solutions require: VA, MA  #mol A  #mol B  VB if MA and MB are known

18. TITRATION
Determination of the concentration of a solution (Mu) by allowing it to react with a standard solution of the titrant of known concentration (Mt).
Start with a known volume (Vu) of the unknown and an indicator that changes color when the rxn is complete.
Deliver titrant to the unknown from a buret until the rxn is over. Record Vt.

19. TITRATION (con’t)
Mt, Vt  #mol titrant --# mol unknown  Mu since Vu is known.
Note that this analysis is based on stoichiometry.

20. CHEMICAL FORMULA A chemical formula can be determined from the
Mass of each element in the formula
% Mass of each element in the formula (% Composition)
Number of moles of each element in the formula
Elemental analysis by combustion

21. CHEMICAL FORMULAS
EMPIRICAL - Contains constituent elements in their correct but smallest integer ratios .
MOLECULAR - Shows all the elements in actual amounts; determined from the empirical formula and molecular mass.