Acid and Base reactions Flashcards
What is a super acid?
Super acids are stronger than sulfuric acids. (capable of protonating H2SO4)
What is a magic acid?
Mixture of Bronsted/Lewis acids: Mix of SbF5/HSO3F (can protonate saturated hydrocarbons)
What is paraffin?
saturated hydrocarbon (no electron pairs left) eg. methane
Caution with HCl
conc. HCl releases highly currosive fume
Caution with H2SO4
- highly hydroscopic
- reaction with water is highly exothermic
- organic substances carbonize upon contact with H2SO4
How is nitric acid produced?
2NO2 + H2O –> 2HNO3 + NO
Features of HNO3
- upon reaction with metal, toxic nitrogen oxides NO are formed
- usage: fertilizers, explosives
Properties of carbonic acid
H2CO3:
- weak diprotic acid
- forms water hardness from dissolved carbonates/sulfates (eg. Gypsum, lime)
- when heated, insoluble sulfates/carbonates are formed
How can water be softened?
dissolved salts must be removed through:
- distillation
- chelating
- precipitation
- ion exchange resin
how can water be softened through chelating?
addition of ligands masking the cations
How can water be softened through precipitation?
addition of substances to precipitate the cations
What is the Haber Bosch production?
Production of ammonia (NH3)
Characteristics of NH3
- colourless gas,
- toxic
- pungent odour
- highly water soluble
uses: fertilizer, explosives
Caution of Hydroxides
very corrosive, damaging to eye
What do hard acids preferably react with?
Hard bases
What are characteristics of hard acids?
small, compact, non-polarizable, high charge
Characteristics of soft acids/bases
large, more diffused distribution of electrons, polarizable
Which one has higher lattice enthalpy, AgF or AgI?
AgI has high lattice enthalpy.
Ag+ is a soft acid, and I- is softer than F-
For Ag X, does X have to be a hard or a soft base for it to be soluble?
Must be hard. Soft- Hard = polar = soluble
What kind of combination of soft/hard acid base must be present for the compound to be soluble?
Soft-Hard = polar = polar
How is the charge density of hard acids?
high charge density (metal ions have high positive charge and small ionic radius)
- d -orbitals do NOT engage in pi bonds
How is the charge density of soft acids?
low charge density (low ionic charge and large ionic radius)
- d-orbitals are available for pi bonding
Where are soft acids usually found?
2nd or 3rd row of transition metals with +1 / +2 charge and filled or almost filled
Is H2O a hard or soft base?
hard
is OH- a hard or soft base?
hard
Is NH3 a hard or a soft base?
hard
is BH3 a hard or a soft acid?
soft
Is NO2- a hard or soft base?
border
is SO3 a hard or soft acid?
hard
is NO3- a hard or soft base?
hard
is SO4 2- a hard or soft base?
hard
What are characteristics of hard bases?
Low charge, high electronegativity and small
Do strength of acid and bases have anything to HSAB?
no
Does HSAB or Acid Base Strength override a reaction?
HSAB
What is HOMO
highest occupied molecular orbital
what is LUMO?
Lowest UNoccupied molecular orbital
How is the interaction of LUMOs and HOMOs for Lewis acid and bases?
HOMO of base intereacts with LUMO of Lewis acid. MOs of adducts are lower in energy (stable)
What kind of orbitals are LUMOs and HOMOs
frontier orbitals
For ionic interaction to occur, must the difference in energy be large or small?
Large
Are Hard - Hard interactions , ionic or covalent?
ionic
Do hard acids have high or low LUMO?
High
Do soft acids have high or low LUMO?
low
Do hard bases have high or low HOMO?
low
Do soft bases have high or low HOMO
high
Are Soft-Soft interactions, ionic or covalent?
covalent (low energy difference between LUMO and HOMO)
General rule for period 2 elements?
Prefer double bonds
Do hard nucleophiles (OH-) react better with hard (H+) or soft electrophile (Br+)?
Hard-Hard combination
Are alkenes soft or hard nucleophiles?
soft
If an alkene is a soft nucleophile, does it have high or low HOMO?
high
Does a soft electrophile have a high or low LUMO?
low
What is activity defined as?
a(X) = f(X) · c(X)
what is f(x) (activity coefficient) equal to when the solution is dilute?
f(x) = 1
As concentration or ionic charge increases what happens to f(x)?
becomes 0
What are general requirements for titrations?
- definite reaction
- fast & quantitive
- titrant must be stable
- end point must be able to be determined
What are common titration methods?
- acid-base titration
- redox titration
- complexation titration
- precipitation titration
What is a bronsted Lowry acid?
Proton donor
Water can act as both an acid and a base. What is this property called?
amphotheric
Definition of concentration
amount of pure compound per volume
if Ka is very large what does it say about the strength of the acid?
the higher Ka, the stronger
How can the strength of an acid be determined?
- strength of H-X bond
similar size = stronger bond (more overlap) = weaker acid - polarity of molecule
more polar = readily ionized = stronger acid
If Y becomes more electronegative in Y - OH bond (oxyacids), does it become a stronger or weaker acid?
the more electronegative Y is, the weaker the OH bond = stronger acid
if more oxygen atoms are added, does it wekaen or strengthen the acid?
the more oxygen atoms, the stronger the acid
- O atoms cause electron deficiency of central atom
- OH bond becomes more polar
What is a Lewis acid?
Electron pair acceptor
As non metals act as Lewis acids, what kind of bonds do they form?
covalent
What kind of bond do basic oxides form in compound?
Ionic
What are cations usually in terms of Lewis acid base theory?
weak Lewis acids
What is the degree of protolysis?
ratio between dissociated and initial amount of an electrolyte
α = [H+]/{HA]0
What is the equation for the degree of protolysis for weak acids?
α = square root (Ka/[HA]0)
What is the degree of titration?
= amount of titrant/ initial amount of analyte
name an indicator for a strong acid -strong base titration
litmus (pka = 6.5)
name an indicator for a weak base - strong acid titration
methyl orange (pka = 3.4)
name an indicator for a weak acid - strong base titration
phenophthalein (pKa = 9.4)
what is a buffer?
- can resist changes in pH when small amounts of acid or base is added.
- consists of weak acid/base and its conjugate partner
What is a buffer capacity?
max. amount of acid/base that can be added before buffer cannot resist pH change
- conc. buffer has a greater capacity
what is a displacement reaction?
volatile/insoluble weak acids/bases are removed by addition of strong base/acid (due to shift in equilibrium
