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MCAT chem > random facts to remember > Flashcards

random facts to remember Flashcards

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1
Q

The equation for an emitted photons energy?

A

E = f x h

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2
Q

diamagnetic vs paramagnetic?

A

all electrons paired - diamagnetic

unpaired electrons - paramagnetic

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3
Q

what is special about group 6 and group 11 electron configurations?

A

they promote s electrons into d orbitals for more stable configuration

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4
Q

what is isoelectronic

A

atoms with the same electron configuration (would be comparing ions)

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5
Q

what is bond dissociation energy?

A

measures bond strength with higher bond dissociation energy indicating a stronger bond

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6
Q

what happens to BP, MP, viscosity, and vapour pressure with increasing IMF’s?

A

BP, MP, viscosity all increase

vapour pressure decreases (since it varies with boiling point. The lower a boiling Point, the higher the amount of evaporation, the larger vapour pressure exerted back down on the liquid)

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7
Q 
what is a 
ionic solid
network solid
metallic solid 
molecular solid?
A

ionic - held together by anion / cation interaction
network - held by covalent bonds
metallic solid - some electrons are free to move around
molecular solid - help by IMF’s!! (therefore weak solids)

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8
Q

metallic solids are best solids for ductile and malleable functions?

A

yes. Ductile = to conduct electricity in a wire

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9
Q

what is heat of formation?

A

the amount of energy to make 1 mole any compound from its elements at standard state

a positive heat of formation means energy is needed to make the compound.

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10
Q

what is the heat of formation and the oxidation number fof O2?

A

heat of formation and oxidation number are both 0!!

elements in standard state don’t have either. (note: oxygen is diatomic in it’s standard state)

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11
Q

do we account for stoichiometry when looking at heat of formation?

A

yes! since heat of formation is for making 1 mole of the compound.

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12
Q

is Br2 (g) in it’s standard state?

A

no since Br2 (and Iodine) are typically liquid at standard conditions not gaseous.

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13
Q

t or f, if we multiply a reaction by a given factor, we multiply that reactions delta H and its E cell by that factor.

A

false, we multiply delta H by that factor but do nothing to E cell.

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14
Q

t or f, WHENEVER WE USE temperature and its not a change in temperature such as in the equation

G = H - TS

temperature is measured in KELVIN

A

true

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15
Q

What kind of phase changes release energy (heat)?

A

phase changes that decrease entropy.

deposition, condensation, and crystalization all release energy to become more ordered.

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16
Q

1 calorie is ___ joules

A

roughly 4

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17
Q

true or false for a given substance

heat of evap = - heat of conden

A

true

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18
Q

what is the area under the horizontal sections of a phase transition curve diagram (x = heat, y = temp)

A

as heat increases along x, temperature increases along y.

At a transition point from lets say solid to liquid (fusion) the temperature does not change cause all heat goes into hanging the phase. The area under this section (a box) is equal to

q = n x delta H of that transition

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19
Q

what is true of an elastic collision?

A

kinetic energy is 100% conserved which is assumed in ideal gases.

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20
Q

what is avogadro’s rule of gases

A

1 mole of gas takes up 22.4 litres.

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21
Q

for real gases what is true of pressure and volume?

A

real gases do contain IMF’s which hold the gas together and decrease pressure

P real < P ideal

Real gases do have mass therefore take up some of the volume in container

V real < V ideal

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22
Q

a weak IMF small gas is likely ideal or real?

A

ideal

23
Q

true or false, smaller molecules effuse quicker. True / false for what reason?

A

true. This is because smaller molecules tend to have higher kinetic speed. Kinetic speed is directly related to rate of effusion.

24
Q

two molecules are at the same temperature. What molecule effuses faster?

A

same temp = same kinetic energy. Therefore smaller molecules will have greater speed at that particular KE and effuse faster.

25
Q

ALWAYS USE KELVIN WHEN NOT USING A TEMPERATURE CHANGE

A

OKAY!

26
Q

what 4 things can we do to increase a forward reaction normally?

A

increase reactant concentration
increase temperature
decrease activation energy
add a catalyst, i.e. ^

27
Q

true or false, stoichiometry effects rate of rxn

A

false, stoichiometry has no effect on kinetics which is the opposite as equilibrium

28
Q

for a unimolecular elementary step and a bimolecular elementary step, what is the order of these reactions?

A

unimolecular step - rate order of 1

bimolecular step - rate order of 2

for any other reaction thats not uni / bi elementary, order must be found experimentally

29
Q

if a reactant effects rate

  1. proportionally
  2. by a factor of 2
  3. not at all

orders???

A

proportionally = 1
factor of 2 = 2
not at all = 0

30
Q

what two things can change the value of the rate constant k

A
  1. increasing temperature

2. decreasing EA

31
Q

what are the units of K for..
first order rxn
second order rxn
third order rxn

A

Units of K must make the right side of the equation = M / second

first order = s^-1
second = M-1 s^-1
third M^-2 s^-1

32
Q

can Keq be negative? if Keq is less than 1 what does that mean?

A

Keq CANT be negative

a Keq 0 - 0.99 indicates reverse reaction is favoured

33
Q

if you add an inert gas to a constant volume container (which already has a gas in it) what occurs do to le chats priniple.

If you add an inert gas to a constant pressure container what happens?

A

add to constant volume, nothing happens (besides an increase in total pressure)

adding an inert gas to a container thats at constant P (therefore V is adjustable) will cause the gas already in the container to shift to the side with more moles.

34
Q

solubility: true or false

  1. all group 1 cations and NH4+, –> NH3 are soluble
  2. all NO3- (nitrate), CIO4- (perchlorate), and CH3CO2- (acetate) salts are soluble
  3. Ag+, Pb++, Pb++++, Hg++, are all insoluble unless paired with the above
A

true.

nitrate, perchlorate, or acetate will make Ag+, Pb++, and Hg++ soluble. Otherwise they wont be.

additionally, Group 1 cations, and NH4+ is also soluble

35
Q

what is the common ion effect?

A

if we add a common ion to a solution that already contains that ion

HX –> H+ + X- (we add more X-)

we decrease the solubility of HX due to le chat

36
Q

what is the complex ion effect?

A

when we have something insoluble such as AgCl (s) we can add it to a solution that contains NH3 to form the soluble Ag (NH3)2.

opposite to common ion effect.

37
Q

what are the 6 strong acids?

A
  1. HI
  2. HBr
  3. HCl
  4. HCIO4
  5. HNO3
  6. H2SO4
38
Q

what is the pH of a solution with 1 x 10^-4 hydroxide solution =?

A

1 x 10^-4 will have a pOH = 4

therefore 14 - 4 = 10

pH = 10

39
Q

true or false, all acid base neutralization reactions go to completion

A

true

40
Q

What salts produce acid in solution and what salts produce base in solution?

A

acid = transition metal cations, Be, Mg, and NH4+

Base: conjugate bases of weak acids (F-, CIO-)

41
Q

how does Cl, Br, Na, K salts effect acidity of a solution?

A

they don’t

acidic salts only: transition metals, Mg, Be, and NH4+

basic salts only: conjugate bases of weake acids (F- and CIO-)

note HCIO is a weak acid
HCIO4 is strong

42
Q

on a titration curve, at what value does pH = pKa (if the titration is using a base titrant on an unknown acid)

A

the point at half the equivalence point when [HA] = [B-]

therefore on the Henderson equation lnQ =0 and pH = pKa

43
Q

[A] x Va = [B] x Vb is used for what?

A

after a titration, we know the concentration and volume of A and we know the volume used to titrate B. Therefore we can use

[A] x Va = [B] x Vb to find [B}

44
Q

Galvanic cells: Where does oxidation and reduction occur? what actually occurs at these sites?

A

anode - oxidation: metal atoms of the anodic electrode lose electrons to become cations in solution. These electrons go up the wire to the cathode.

cathode - reduction: incoming electrons from the anode react with cations in the solution (reduce) to form metal solid making the cathodic electrode grow.

45
Q

Galvanic cells: which direction does e flow go?

A

anode to cathode –> this is the same direction as abbreviated cell notation.
anode | anode solution || cathode solution| cathode

46
Q

Galvanic cells: Which direction does ions move in the salt bridge. If the salt bridge is removed what happens?

A

cations move to cathode
anions move to anode

if you remove the salt bridge, charge builds up on each side (cathode becomes more negative since cations are being reduced and anode becomes more positive since solids are being oxidized)

This resembles a capacitor!! separation of charge!!

47
Q

what is E cell of spontaneous reactions?

A

E cell must be positive

delta G = - nFE

48
Q

What is true of a reaction with a very negative reduction potential and a very positive reduction potential.

X+ + e –> X (s)

A

a vert positive reduction potential means the reactant is a strong oxidizing agent (it wants to get reduced)

a very negative reduction potential means the product is a strong reducing agent (since it’s oxidation is favourable)

49
Q

in a concentration cell, two identical electrodes are submerged in different concentrations of ion. Which is the cathode?

A

the one with higher concentration since, at the cathode, electrons are taken up to remove content from solution.

when concentrations are equal then the rxn stops

50
Q

what is true of the half equivalence point of a redox titration?

A

[oxidized] = [unoxidized]

[reduced] = [unreduced]

Therefore E = E (not)

E = E(not) - (RT/nF)lnQ (where Q = 1)

51
Q

what is an electrolytic cell?

A

uses a battery / voltage to generate current that induces an unfavourable redox rxn to occur

52
Q

what is the main difference between galvanic and electrolytic cells?

A

galvanic cells –> anode = (-) and cathode = (+)

electrolysis –> anode is (+) and cathode is (-)

think electrons want to go to positive (therefore in spontaneous galvanic cells they go to the positive cathode)

in electrolysis, they are being forced to go somewhere they don’t wanna go so therefore the cathode is negative.

direction is ALWAYS ANODE TO CATHODE. Therefore the signs of them change rather then direction.

53
Q

Q = I x t

explain how this equation can get you to get mass of a salt in an electrolytic cell.

A

if you are giving the half reactions + the time the cell run for + the current in the wire then

the total amount of charge that ran through the wire is given as Q = I x t

then we use faradays constant (95,000 C/mol) to get moles of charge.

then we use stoichiometry to determine moles of reactions X and Y

then with moles of X or Y we use molar mass to find mass used in the rxn.

MCAT chem (11 decks)

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