FINAL study guides Flashcards
A spontaneous reaction implies…
- ΔK > 1
- ΔG < 0
- ΔSuniverse > 0
- E∅ > 0
- NOT: ΔHrxn < 0
What does normal boiling pt / normal freezing pt signify?
Normal ⇒ 1 atm pressure
When does boiling occur (regarding the vapor pressure of the liquid)?
When vapor pressure (v. p.) of liquid equals external pressure
- for normal boiling point: Vpressure = 1 atm.
- ΔHvap = P
What are “standard conditions”?
- 1 M aqueous species
- P = 1 atm
dissolution (solubility/ionization) reaction
solid <–> aq + aq
- ex: AgI (s) <–> Ag+ (aq) + I- (aq)
- ex: Fe(OH)3 (s) <–> Fe3+ (aq) + 3(OH-) (aq)
dissolution (solubility/ionization) reactions can go in ___ direction(s)
forwards and backwards directions
<—–>
precipitation reaction
(aq) + (aq) –> solid
- Ag+ (aq) + I- (aq) –> AgI (s)
- Fe3+ (aq) + 3(OH-) (aq) –> Fe(OH)3 (s)
precipitation reactions go in __ direction(s)
ONLY forwards direction
—–>
water auto-ionization reaction (water dissociation reaction)
H2O (l) <—> H+ (aq) + OH- (aq)
- Kw = 1 x 10^14 @ 25C
will a buffer form?
CA/CB in comparable amounts
- if not comparable, do SICE table
SA/WB or WA/SB, SICE, CA/CB in comparable amounts?
is the aqueous solution (compound) acidic?
1) cancel out ions from SA/SB
2) are the remaining ions cations (+) or anions (-)?
- cations (+) = acidic
- anions (-) = basic
acid with smallest pKa corresponds to the _____ with largest ____ because pKa + pKb = 14 for conjugates.
- conjugate base
- pKb
The larger the pK value, the ___ that species is
- weaker
pH at equivalence point of SA/SB
pH = 7
pH at equivalence point of a SB/ WA
pH > 7
pH at equivalence point of SA/WB
pH < 7
∆G = 0…
- at phase transition
- at equilibrium
- Q = K
- boiling
- ∆H = T∆S
For an exothermic reaction…
reaction loses heat –> ∆Hrxn < 0
entropy of surrounding ↑ –> ∆Ssurr > 0
boiling point increases w/ increasing…
- increasing molar mass
- increasing polarity
- increases greatly w/ hydrogen bonding
What are the general properties of a water-soluble molecule or ion?
- monovalent charge (charge = ±1)
- presence of polar bonds
- if “long; several hydroxyl groups (OH) throughout
- number of carbons ≤ 5 (linear chain)
- heterocyclic rings ( nitrogen or oxygen as well as carbons at vertices of hexagon)
SO3 gas dissociation reaction:
2 SO3 (g) → 2 SO2 (g) + O2 (g)
if a question asks about a “shift in equilibrium”, you need…
K and Q and to compare
(multi-step reaction energy plot): the rate-limiting step usually…
involves the larger activation energy “barrier”
- largest Ea / largest “hump”
(multi-step reaction energy plot): How many transition states are involved?
how many humps on the graph
(multi-step reaction energy plot): Which step has the largest forward rate constant?
- largest forward rate constant = smallest activation energy (smallest Ea)
breaking bonds…
- requires energy
- endothermic
- ΔH > 0
making bonds…
- releases energy
- exothermic
- ΔH < 0
Which species are likely soluble in water? is another way of asking
Which pairs of species could, in principle, hydrogen bond with each other in a solution
Which of these gases could be liquefied (by pressure alone) at 25C…?
any gas w/ Critical Temp. (Tc) > 25C
Which of these gases could be liquefied (by pressure alone) at 25C…?
any gas w/ Critical Temp. (Tc) > 25C
ALL equilibrium constant questions require…
ICE TABLE
nuclear reactions (ex: beta-plus decay) are ___ order
1st order
any natural or molecular compound (glucose, sucrose, alcohol, NH3), “I” (number of ions) always =…
1
cathode =
reduction = oxidizing agent
anode =
oxidation = reducing agent
the strongest base has…
the largest Kb, the smallest Ka
electrolyte
a compound that conducts an electric current when it is in an aqueous solution or melted
- covalent, molecular
electrolytic (i) = ?
(i) = 2
non-electrolytic (i) = ?
1
as Ksp increases, molar solubility…
increases
as Ksp decreases, molar solubility…
decreases
(reaction profile): slow =
tall
(reaction profile): fast =
small
condensation and deposition = ΔS =
ΔS < 0
ΔS = ? for:
solid –> liquid, liquid –> gas, solid –> gas
ΔS = (+)
How could the buffering capacity be improved?
increase mols of acid and base
E = () = spontaneous
E = (+)
E = () = non spontaneous
E = (-)
the second law of thermodynamics states…
entropy (ΔS) of the universe = (+)
- ΔS(surroundings) = -ΔS(system)
T/F: for the reversible process, ΔS(surroundings) = -ΔS(system)
TRUE
T/F: for any spontaneous process, ΔS(universe) > 0
TRUE
T/F: the entropy of the universe is conserved in any process
FALSE
if a solution decreases in temp…ΔH = ?
- endothermic = ΔH = (+)
if a solution dissolves….ΔS = ?
- dissolve = disorder = ΔS = (+)
the oxidation state of a pure element is ALWAYS..
zero (0)
the substance that is oxidized or reduced are ALWAYS
reactants
if something is being oxidized or reduced it pertains to….
the element/ion
if something is an oxidizing agent or reducing agent it pertains to…
the whole compound
