Module 4 content Flashcards
(23 cards)
How do the states of substances in equilibrium affect Kc?
Solids and liquids are omitted
Only gas or Aq concentration included
Mole fraction
Number of moles of A/ total number of moles in gas mixture
Sum must equal 1
Partial pressure
Mole fraction of A x total pressure P
Sum of pp= total pressure
Kp values
Written like Kc but with lowercase p before brackets
p= eq pp
kPa, Pa or atm
Only includes gases
When does the value of K(p) change?
At a set temp, k does not change
Exothermic:
Higher temp= lower K
Lower yield of products
Ratio of Kp is too high so pp of products must decrease and reactants increase= eq shift to left
Opposite for endo
Bronsted-Lowry acid and bases
Acid is proton donator
Base is proton acceptor
Conjugate acid-base pairs
2 species that can be interconveerted by transferring a proton
Left= acid 1, base 2
Right= acid 2, base 1
Types of acids
Mono, di and tribasic= number of H ions
pH calculation
pH=-log(H+(aq))
H+ calculation
H+=10^-pH
Calculation of strong acids pH
Release all H+ so calculated directly from concentration of H+
Dissociation of a weak acid
HA–> H+ +A-
Ka value
(H+)(A-)/(HA) for a weak acid
Ka and pKa
pKa= -logKa
Ka=10^-pKa
pKa & Ka values interpretation
Stronger acid= higher ka= lower pKa
Approximations when caculating pH of weak acids
1) The acid conc at eq is the same as the acid we are using
2) The conc of H+ ions is equal to A- (anions)
Ka simplified expression
(H+)squared/ (HA)
Ph calculations of a weak acid
(H+)= square root of (Ka x(HA))
Kw
Treat water as a weak acid in Ka
Kw= (H+)(OH-)
1 x 10^-14 mol2dm-6
Calculating pH of a strong base
Alkali that completely dissociates in water
Monoacidic= realease 1 OH-
Use conc of base and Kw
Calculating pH of weak bases
Similar method to weak acids
What is lattice enthalpy?
The measure of strength of ionic bonding in a giant ionic lattice
Energy change that accompanies 1 mole forming from gaseous ions
Exothermic—> negative
