Unit 4 Flashcards
K
equilibrium constant, do not include solids in equation
le Chateliers principle
When a chemical system at equilibrium is disturbed in a change in a chemical property, the system adjusts in a way that opposes the change
Change in [ ]
System will shift opposite way
Thermal energy
System will shift towards the thermal energy q
Decrease in volume (increase in pressure)
System will shift towards the side with less gas molecules
What will not effect le Chateliers principle
Adding inner gasses, catalysts
Q=K
System is at equilibrium
Q>K
System must shift left to reach equilibrium
Q
System must shift right to reach equilibrium
Assumptions
If more than two decimal places over
Arrhenius theory
Acids produce H+ ions when dissolved. Bases produce OH- when dissolved
Bronsted- Lowry theory
Acids are proton (H+) donors, bases are proton receivers
amphoteric/ amphiprotic: a substance that can act as a B-L acid or base at the same time
Conjugate acid pairs
A pair of substances who’s molecular formula differ by one H+
Strong acid
100% ionized
Monotropic- releases only one H+
Ditropic- releases only two h+
Triprotic- releases only 3 H+
HCl, HBr, HI, H2SO4, HNO3, HCLO4
Weak acid
An acid that is less than 100% ionized, in reality, much less than 50%
Relative strength
The stronger the acid is, the weaker the conjugate base is etc.
Kw
[H+][OH-]= 1.0X10^-14
pH+pOH
=14=PKw
pH
-log^[H+]
pOH
-log^[OH-]
Strong bases
100% ionized
Group 1 metal hydroxides + some others
% ionization
(concentration of ion ionized/ concentration of solution) X100
Measuring pH
litmus paper ( red= acid, base= blue)
Phenolphalein: colorless—–> 8-10
pH meter—-> based on electrical conductivity
Haber processes
- Used to make ammonia, optimal conditions are in a closed system with a catalysts and very high temperatures
Ka X Kb
Kw
Salt hydrolysis
Reaction of ions with water to produce acidic or basic solutions
a) if salt contains ions from strong acid and strong base the results will be neutral
b) If the salt contains the conjugate acid of a weak base, the resulting solution will be acidic
c) If the salt contains the conjugate base of a weak acid then the resulting solution will be basic
d) When a salt contains ions from a weak acid and a weak base, the values of Ka and Kb are compared to determine acidity
e) Amphoteric ions- Compare the values of Ka and Kb
f) Metal oxides with water- bases
Non metal oxides with water- acids
Titration
To determine the amount of a specific chemical in a sample by adding a known amount of another substance
Equivalence point
The point where the moles of acid equals the moles of base
End point
The point where the indicator changes colour and the titration ends, usually just past the equivalence point
The first law of thermodynamics (law of conservation of energy)
Energy can only be transformed, not created or destroyed
Enthalpy changes and spontaneity
Exothermic reactions -H have a tendency to occur spontaneously
Entropy, S
Degree of randomness in a system
Predicting the signs of S
Gasses» solutions > liquids» solids. If the right side has more random states, S is positive.
Second law of thermodynamics
When ever a spontaneous event takes place in our universe, it is accompanied by an overall increase in entropy
Third law of thermodynamics
An absolute 0, the entropy of a perfectly ordered pure crystalline substance is zero
Standard entropy (S)
Sum of Sf products- sum of Sf reactants
Gibbs free energy
Maximum energy that is available to do work
G
H-TS
Gfinal- G initial
Dynamic equilibrium
Forward and reverse rates are equal
Solubility equilibrium
Salt no longer appears to dissolve at the saturation point, but on microscopic scale dissolving and crystallizing are still occurring
Phase equilibrium
liquid- gas
Solid- liquid
-H, +S
G is non spontaneous (+)
+H, -S
G is spontaneous (-)
Spontaneous G sign
-
+H, +S
G is only negative at high temps
-H, -S
Only spontaneous at low temps
