Chemical Equilibrium Flashcards
1
Q
Ksp
A
- dissosiation constant
- higher Ksp= more soluble compound
- experimentally found, obtained from a chart
- coefficients turn into exponents
- ICE tbl (MOLES) to find
- NO SOLIDS OR PURE LIQUIDS
concentration of reactant(s) - [A+]^a[B-]^b
2
Q
Common Ion Affect
A
- more of ions already in solution added lowers solubility of added reactant
- ions already present limits dissociation of more of same ions being added
- Ksp decreases, equilibrium shifted to reactants side of reaction
3
Q
Acid in water
A
- strong completely dissociates
- will form water with OH and shift equilibrium to products side
4
Q
Q < Ksp
A
- less than
- no ppt formed
5
Q
Q > Ksp
A
- greater than
- ppt formed
6
Q
Q
A
- reaction quotient
- relative amount products and reactants present
- changes as approach equilibrium
- [X]^x[Y]^y
7
Q
2 types of gravimetric analysis
A
- precipitation
- volatilization
8
Q
Precipitation
A
- solid generated from liquid phase medium
- precipitate “falls out” of supernatant (water above) via the use of excess of reagent
9
Q
Volatilization
A
- gas comes out of solid or liquid medium
10
Q
Precipitating agents
A
- specific
-selective
11
Q
Specific precipitating agent
A
- reacts w/ only one chemical species
12
Q
Selective precipitating agent
A
- reacts w/ limited # of chemical species
13
Q
4 qualifications to make good ppt
A
- easily filtered/washed (larger particles)
- low solubility
- unreactive w/ atmosphere
- known composition
14
Q
Colloidal suspension
A
- v small [(10^-7 - 10^-4) cm diameter] particles
- hard to filter/centrifuge
- fix via recrystallization
15
Q
Crystalline suspension
A
- larger particles
- settle spontaneously
- easy to centrifuge and filter
16
Q
Goal and methods to control particle size (4)
A
- goal: maximize crystalline ppt particles
- recrystallization
- slow addtn of ppt agent
- using dilute solutions
- induce nucleation and particle growth
17
Q
Coprecipitation
A
-when soluble compound removed from solution during ppt formation
- minimize via recrystallization, washing of ppt, or increase of analyte concentration
18
Q
Surface adsorption
A
- coprecipitation issue
- ions stay on surface of solid
- wash and decant to fix
19
Q
Mixed crystal formation
A
- one of ions in solid crystal lattice replaced by another
- caused by formation occurring too quickly
- recrystallize or digest ppt to fix
20
Q
Occlusion
A
- crystals grow too fast and trap counterions
- use dilute solutions slowly or recrystallize to fix
21
Q
Mechanical entrapment
A
- crystals grow too close together and grow together/ trap pockets of solution
- use dilute solutions slowly or recrystallize to fix
22
Q
Recrystallization
A
- boil ppt in supernatant/ wash
- allow to cool slowly and bigger crystals form
23
Q
Like dissolves
A
like
24
Q
Like attracts
A
like
25
Q
Polyatomic ions in solution
A
- stay as polyatomic ions in solution, no further dissociation
26
Q
Ksp increase
A
- equilibrium shifts towards products side of reaction
27
Q
Typical rxn of ions of interest
A
Ca(OH)2 (s) ——–Ca 2+ (aq)+ 2 OH - (aq)
