exam 2 chem 1230

when does a precipitate form?
when the attractive forces between ions are large
what are the exceptions for I, Cl, and Br?
Ag, Hg, Pb, Cu, Ti
what are the exceptions for SO4?
Ca, Sr, Ba, Pb
what are always soluble?
NH4, group 1A, NO3, ClO4, Clo3, C2H3O2
solution
homogenous mixture of 2+ substances
solvent
major proportion
solute
minor proportion
colligative properties
affected by concentration of particle the solute contirbutes to the solution
what are examples of colligative properties?

osmotic pressure

vapor pressure lowering

boiling point elevation

freezing point depression

 

colligative molality
change in freezing point or boiling point of a solvent when solute is added
what is the equation for colligative molality? (Mc)
Mc = i x m
how do you find molality and what are the units?
moles of solute / kg of solvent
what is i?
vant hoff factor; # of particles produced when a solute dissolves
what is the equation for delta T?
delta T = Kf * Mc
what is Kf?
the freezing point depression constant of solvent
what are the properties of lauryl acid?
non hazardous but prolonged contact may cause skin irritation
what equipment is used in experiemnt 8?

crystallization dish

graduated cylinder

beaker

thermometer

tongs

spatula

hot plate

when is equilibrium established?
when the rates of the forward and reverse reactions are equal
what are the properties of HCl?
corrosive, irritant, use fume hood, injures eyes and skin
what are the properties of AgNO3?
dark spots
what is the effect of raising temperature with respect to Le Chateliers principle?
equilibirum shifts to the higher energy side
what are the reactions studied in experiment 9?

CoCl4^2- + 6 H2O -> Co(H2O)6^2+ + 4 Cl^-

Fe^3+ + SCN^- -> FeSCN^2+

when are reactants favored? products?

when K is low

when K is high

what are titrations?
stoichiometric volume of one reactant of known concentration (titrant) is required to react with another reactant of unknown concentration (analyte)
how is the concentration of the analyte determined?
from the concentration of the titrant and stoichiometry of reaction between them
what is in the buret?
titrant
what is in the flask?
analyte
what is in indicator
a substance that changes color near the equivalence point
how is an indicator chosen?
when the equivalence point is near the end point
what is the endpoint?
point at which the color change occurs
what should you consider when setting up a titration?

buret measured to nearest .01 mL

make sure no air bubbles in buret tip

condition buret

fill buret below 0 mark

close stopcock

what happens if you dont condition the buret?

the volume of titrant will increase

the moles of analyte will be overestimated

what happens if you condition the flask with analyte?

increase in volume of titrant

overestimation of moles of analyte

mass %
moles of acid / moles of base x 100
how do u go from moles to mmol
1 mol = 1000 mmol
what is the difference when doing conjugates?
a H+
conjugate base of an acid
remove an H+
conjugate acid of a base
add H+ to base
what subsances are corrosive?

acetic

Nh3

Hcl

Naoh

what substances are irritants?

acetic

NH3

HC;

how do u find [H3O+] given pH?
H+ = 10^-pH
how do u find pH given [H+]
pH = log[H+]
enthalpy
amount of heat energy absorbed at constant pressure
entropy
number of ways energy can be distributed in a system
system
part of universe being studied
surroundings
part of universe that interacts with system being studied
spontaneous
lowers energy of system
nonspontaneous
amount of energy supplied to cause process to occur
heat of reaction
when reactants react completley at STP
electrodes
metal strips
cathode
reduction
anode
oxidation
saltbridge
allows ions to travel from one 1/2 cell to other
voltmeter
calculates potential difference between oxidizing and reducing agents (mV -> V)
how do you find Ecell
Ecell = Ecathode – Eanode
if H < 0 and S > 0
spontaneous
if H > 0 and S < 0
non spontaneous
H < 0
exo
H > 0
endo
S < 0
spontaneous
G > 0
nonspontaneous
x

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