CHEM 1150 Lecture Notes - Lecture 7: Limiting Reagent, Molar Concentration, Ammonium Sulfate
She only cares about balancing atoms
-
Steps:
Translate the statement
1.
Balance the atoms
2.
Adjust the coefficients
3.
Check the atom balance
4.
Specify states of matter
5.
General tips and hints:
Start w/ atoms in most complex substance (and end w/ simplest
substance like H2)
§
Take one element at a time, working left to right (or vice versa)
§
Balance oxygen in a combustion reaction last (it will occur in
multiple reactants or products)
§
Polyatomic ions that appear on both sides of equation should be
balanced as independent units
§
It is useful to use fractions when balancing, but make it clear when
multiplying entire equation by the denominator!
§
Check your atoms!
§
○
-
Stoich
Molar ratio: 1 of CO2for every 2 moles O2(get out of the equation)
○
Limiting reagent/ reactant: g of reactant of MM * (# of mole of product of
interest/ # mole of reactant) and then compare the two to determine
limiting reactant
Multiply moles of product by product of interest by its MM to
get its theoretical yield
□
Use LR to use how much ER is used and how much is left over
§
Percent yield= (actual yield/ theoretical yield)*100
Side reactions
A+B (reactants) --> C (main product)
Or think of as down arrow to D (side products)
◊
®
□
§
○
-
Molarity
M= moles/ liter
○
M1V1= n = M2V2
○
-
Ions in water
Solute:
○
Solvent:
○
Ex. 5 mol ammonium sulfate dissolved in water
(NH4)SO4(s) --> 2NH4+(aq) + SO42-(aq)
Good to understand for test: oxygen is the negative part of
the water, and H is the partial/ positive part (b/c H2O
supposed to be over -->)
□
Solve for ions (products) using stoich.□
§
○
-
Types of reactions:
Precipitation reactions:
Double displacement
§
○
Acid base reaction
Gas evolution reaction (bubbles formed)
Look up/know common gases evolved (made) in these types
of rxn's: H2S, CO2, SO2, NH3
□
§
Make a salt (aq) and water (l)
§
○
Oxidation reduction reactions (redox reactions)
Decomposition/ combination reactions
§
Single displacement reactions
§
Combustion reactions
§
○
Predicting reactions
○
Titration
Neutralization reactions (w/ burette)
○
○
Solubility rules
Water is universal solvent
§
Thing in excess: solvent
§
(aq)= soluble (dissociates)
Group 1A: alkali metals: will always be soluble no
matter what
Also NH4+, NO3-, ClO4-
◊
®
Cl-, Br-, I-soluble with Ag+, Pb2-, Cu+
®
CO32- and PO43- insoluble EXCEPT alkali metals and NH4+
®
OH-insoluble EXCEPT alkali metals, NH4+, Ca2+, Sr2+, Ba2+
®
S2- insoluble EXCEPT alkali metals, alkali earth metals,
and NH4+
®
§
Aqueous ionic reactions
Molecular equation: shows all reactants and products intact,
as they originally are
2AgNo3(aq) + Na2CrO4(aq) ---> Ag2CrO4(s) +
2NaNO3(aq)
®
◊
Total ionic equation: shows all soluble ionic substance
dissociated into ions
2Na+(aq) + 2NO3-(aq) + 2Na+ (aq) + CrO42-(aq) -->
AgCrO4(s) + 2Na+(aq) + 2NO3-(aq)
®
◊
Net ionic equation: eliminates spectator ions, leaving actual
chemical change occurring
2Ag+ + CrO42-(aq) --> AgCrO4(s)
®
◊
§
○
-
Oxidation reaction
General rules:
For an atom in its elemental form, its oxidation # is 01)
For a monoatomic ion, its oxidation # is its ion charge
The sum of oxidation # for atoms in a compound = 0 unless
polyatomic ion, when the sum would equal the charge of the
polyatomic ion
1)
2)
○
Rules for specific atoms or periodic table groups:
For group 1, O.N. = +1 in all compounds1.
For group 2, O.N. = +2 in al compounds2.
For hydrogen, O.N. = +1 in combination w/ non-metals and -1 in
combo w/ metals and Boron
3.
For fluorine, O.N. = -1 in all compounds4.
For oxygen, O.N. = -1 in peroxides, and -2 in all other compounds5.
In group 7A (17), O.N. = -1 in combination w/ metals but something
else when in combination with polyatomics or non-metals
6.
○
If 2 of a compound, don't get tripped up
○
What loses e- is oxidized (b/c becomes more +), what gains e- is reduced
(b/c becomes more -)
What loses e- is reducing agent (oxidized), what gains e- is oxidizing
agent (reduced)
§
○
LEO says GER
Loose e- Oxidized
§
Gain e- Reduced
§
○
-
Chapter 4: Chemical rx's and stoich: chem rxn's and
stoich
Monday, February 5, 2018
10:46 AM
Document Summary
Chapter 4: chemical rx"s and stoich: chem rxn"s and stoich. Start w/ atoms in most complex substance (and end w/ simplest substance like h2) Take one element at a time, working left to right (or vice versa) Balance oxygen in a combustion reaction last (it will occur in multiple reactants or products) Polyatomic ions that appear on both sides of equation should be balanced as independent units. It is useful to use fractions when balancing, but make it clear when multiplying entire equation by the denominator! Molar ratio: 1 of co2 for every 2 moles o2 (get out of the equation) Limiting reagent/ reactant: g of reactant of mm * (# of mole of product of interest/ # mole of reactant) and then compare the two to determine limiting reactant. Multiply moles of product by product of interest by its mm to get its theoretical yield.
