diploma studying Flashcards
thermochemistry
what is Q=mcΔt mean, and what do the individual elements represent?
-used to calculate heat transferred in a process with no phase change
- Q = quantity of heat transferred into the system
m = mass (g)
c = specific heat capacity
Δt = temperature change
thermochemistry
what is the origin of chemical bond energy?
(majority of biosphere) is derived from solar energy
- energy required to break bonds
- energy released when bonds break
thermochemistry
what is enthalpy?
- change in potential energy between reactants and products
- represented by ΔH (or ΔrH)
thermochemistry
what is molar enthalpy?
- enthalpy per mole of specified substance
- represented by ΔH, or ΔHm
- units in kJ/mol
thermochemistry
how do you find amount of energy released or absorbed in reaction (equation)
ΔH = nΔrH
ΔH = enthalpy change
n = #of moles of specific substance
ΔrH = molar enthalpy
thermochemistry
how do you find standard enthalpies of formation
ΔrHº = Σ(nΔfHº)products - Σ(nΔfHº) reactants
Σ = “sum of”
thermochemistry
what is calorimetry, the equation, and individual representations?
- energy lost/gained by system observed by (equal to) changes in water temperature
ΔH = -Q = -mcΔt
m = mass of water
c= specific heat capacity of water
=Δt is change in water temperature
thermochemistry
what is a bomb calorimeter
- different material other than polystyrene used
- heat absorbed must be accounted for
formula: nΔrH = CΔt
C=constant, heat capacity of calorimeter
no need for mass
thermochemistry
states of water in organic reactions
- photosynthesis and cellular respiration both produce/consume LIQUID water (closed systems)
- in open systems (e.g. combustion), GASEOUS water will be produced
thermochemistry
ΔH, endothermic and exothermic
ΔH positive = endothermic
ΔH negative = exothermic
photosynthesis is endothermic, while combustion and cellular respiration is exothermic
thermochemistry
what is activation energy
- Ea, minimum collision energy to produce a successful reaction
- (KMT) = need sufficient speed and orientation to occur through collisions
thermochemistry
breaking/forming bonds in relation to endothermic and exothermic reactions
- exothermic = products contain less potential energy than reactants
-endothermic = products contain more potential energy than reactants, require more kinetic energy to create activated complex (extra energy stored in bonds of products)
thermochemistry
catalysts and their effects
- cause rate of reactions to increase by providing an alternate pathway (less energy needed)
does NOT affect value of ΔH, change reactants/products, or get consumed
electrochemical changes
what is oxidation and reductions
oxidation: loss of electrons, substance is oxidized
reduction: gain of electrons, substance is reduced
electrochemical changes
what is a redox reaction
two processes do not occur in isolation
net reaction, “reduction-oxidation reaction”
electrochemical changes
what are oxidizing and reducing agents?
oxidizing agent: GAINS electrons (reduced), causes another substance to get oxidized
reducing agent: LOSES electrons (oxidized), causes another substance to get reduced
electrochemical changes
what is disproportionation?
- redoc reaction where the SAME substance functions as both the RA and the OA
electrochemical changes
what is an oxidation #, and relation to oxidation and reductions
- positive or negative number, allows you to determine the movement of electrons in a reaction
increase: substance is being oxidized
decrease: substance is being reduced
H is ALWAYS +-1, O is always -2
*easiest way to determine if a reaction is a redox rxn or not
electrochemical changes
what is the rule of spontaneity?
if the OA is above the RA on a table of half-reactions, the reaction is spontaneous. If not, it is non spontaneous
electrochemical changes
balance out redox reactions
(from half reactions)
- write half reactions
- multiply coefficients to balance electrons
- add half reactions to obtain balanced net reaction
electrochemical changes
balance out redox reactions (creating own half reactions)
- balance all molecules except O and H
- Add H2O to balance O
- Add H to balanced H
- Balance electrons
- write out half reactions
- multiply one half reactions to match electrons in other half reaction
- add together to obtain net reaction
electrochemical changes
balance out redox reactions (from OA and RA)
- identify OA and RA
- balance electrons
- balance primary atom
- balance oxygen with H2O
- balance H
electrochemical changes
what is a voltaic cell
-spontaneously reaction to produce electricity
E net: positive
electrochemical changes
what is an electrolytic cell
- uses electricity to cause non spontaneous reaction (electrical>chemical energy)
E net: negative
electrochemical changes
what is the electrode
solid in half cell
electrochemical changes
what is the anode
electrode where oxidation occurs (SRA reacts)
voltaic: negative charge
electrolytic: positive charge
electrochemical changes
what is the cathode
where reduction occurs (SOA reacts)
voltaic: positive charge
electrolytic: negative charge
electrochemical changes
what is an anion and cation
anion: negative ion, moves to anode
cation: positive ion, moves to cathode
electrochemical changes
what is a salt bridge/porous cup
- barrier which keeps solutions of voltaic cells apart, but allows ion flow
electrochemical changes
what is an electrolyte
- substance that conducts electricity when dissolved in water
- solutions in both cells
electrochemical changes
what is a power supply
electronic device that replaces a battery
- drives electrolysis reactions
electrochemical changes
what is the external circuit
wires (and voltmeter) that are used to connect anode to cathode
electron flow from the anode to the cathode
electrochemical changes
what is the line notation for cells
anode|anode electrolyte||cathode electrolyte|cathode
electrochemical changes
what is the chloride anomaly
when H2O ( in presence of CL) is both the SRA and SOA, chloride will become the SRA (anode rxn)
electrochemical changes
what are standard reduction potentials
Erº, measured to the standard hydrogen half cell (Erº=0.00V)
electrochemical changes
how to calculate standard cell potential
Eºnet = Erºcathode - Erºanode
positive: spontaneous
negative: non spontaneous
organic chemistry
what are organic compounds, and exceptions?
- molecular compounds of carbon
exceptions: oxides, and ionic compound containing carbon
organic chemistry
organic compound nomenclature
1-meth
2-eth
3-prop
4-but
5-pent
6-hex
7-hept
8-oct
9-non
10-dec
organic chemistry
difference between unsaturated and saturated hydrocarbons
saturated: single bonds
unsaturated: double/triple bonds
organic chemistry
hydroxyl functional group
R-O-H
alcohol
organic chemistry
carboxyl functional group
- carboxylic acid
r-(o=c-o)-h
*where r is bonded to the c atom
organic chemistry
ester linkages`
-SINGLE bonded oxygen bonds to another hydrocarbon (cutoff!)
-r1(o=c-o)-r2
*where r1 is bonded to the c atom
organic chemistry
halogens
-halogen atom (G17) bonds to hydrocarbon
- R-X, x= halogen
organic chemistry
what is a structural isomer
- same molecular formula, but different structure
- similar chemical properties but different physical properties
organic chemistry
what is an addition reaction
-diatomic molecules added across double/triple bond
- becomes more saturated (e.g. double–>single)
organic chemistry
what is a substitution reaction
- atom replaces another atom in a molecule
- often require the presence of light
organic chemistry
what is an elimination reaction
- molecule is removed, create double bond
- water or hydrogen halide is commonly produced
-(reverse addition)
organic chemistry
what is an esterification reaction
- water is eliminated (created) to make an ester
- carboxylic acid + alcohol = ester + water
organic chemistry
what is a combustion reaction
- hydrocarbon or alcohols react with oxygen to produce CO2 and water
organic chemistry
polar vs non-polar structure
polar = asymmetrical
nonpolar = symetrical
what is the haber process
production of ammonia
n2 + 3h2 <-> 2NH3
what does shift left/right mean
right: more products formed
left: more reactants formed
le chatliers principle: temperature
increase: shift endothermic right, exothermic left
decrease: shift endothermic left, exothermic right
le chatlier’s principle: concentration
shift right. (add to right): increase reactant, decrease product
shift left (add to left): increase product, decrease reactant
le chatlier’s principle: volume/pressure
increase: shift to side w more moles of gases
decrease: shift to side w less moles of gases
what is the equilibrium constant?
kc, for aA+bB=cC+dD
[C]c[D]d/[A]a[B]b
affected by temperature
kc generalizations
kc >1 = products favoured
kc = 1, relatively the same concentration
kc < 1, reactants favoured
what is a bronsted-lowry acid and base
acid: proton donor
base: proton acceptor
what does polyprotic mean
conjugate base can continue to give away protons (H+), can be determined by # of H’s
equilibrium position in relation to acid base strength
check side with stronger acid/base, weaker side will be favoured
conjugate acid/base pairs + equilibrium position
- all reactions have two conjugate acid-base pair
differ by one proton - if acid higher than base, favours products (>50%)
- if acid lower than base, favours reactants(<50%)
what is an amphiprotic substance
can act as an acid or a base
what is a buffer
-mixture of weak acid and conjugate base
- addition of acid/base will be neutralized to water, by the opp (acid/base, base/acid)
what is the equivalence point
same # of mole of titrant added a tere were moles of sample
>7 = SB-WA
<7 = SA-WB
=7, SA-SB
ph and h3O formula
ph=-log[H3O]
[H3O]=10^-ph
responsible for acidic properties
pOH and OH formula
pOH=-log[OH]
OH=10^-pOH
responsible for basic properties
what is Kw
-equilibrium constant for ionization of water
-kw=1.00x10^-14. (=[h3O][OH])
what is Ka
- equilibrium constant for reaction of acid with water
Ka = [H3O][A-]/HA (prod/reactant)
what is Kb
- equilibrium constant for reaction of base with water
- kb = [OH][HA]/[A] (prod/reactant
