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mcat > gchem 2 > Flashcards

gchem 2 Flashcards

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MCAT flashcards
1
Q

What is convection?

A

fluid movement caused by hotter portions of a fluid rising and the cooler portions of the fluid sinking

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2
Q

What is radiation?

A

electromagnetic waves emitted from a hot body into the surrounding environment

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3
Q

What is a black body radiator?

A

theoretically perfect body that absorbs all energy incident upon it and emits 100% of this energy as electromagnetic radiation

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4
Q

What is conduction?

A

molecular collisions carry heat along a conduit

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5
Q

What is heat capacity?

A

the amount of energy a system must absorb to give a unit change in temperature (J/K or cal/degrees celcius)

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6
Q

What is the formula for heat capacity?

A

C = q/∆T

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7
Q

What is the formula for specific heat?

A

q=mc∆T

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8
Q

What is the specific heat of water?

A

1.0 cal/g ̊C

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9
Q

What is the purpose for calorimeters?

A

To calculate enthalpy change

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10
Q

How to solve coffee cup calorimeter problems

A

q=mc∆T

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11
Q

How to solve bomb calorimeter problem

A

q = C∆T

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12
Q

Which type of calorimeter provides constant pressure and which provides constant volume?

A

bomb -constant volume

coffee- constant pressure (atmospheric)

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13
Q

What is pressure - volume work?

A

change in volume at constant pressure

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14
Q

On a pressure vs. volume graph, what represents the pv work?

A

The area under the curve

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15
Q

What is the first law of thermodynamics?

A

energy can neither be created or destroyed

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16
Q

work done on the system is ___, work done by the system is ___

A

positive, negative

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17
Q

What is the second law of thermodynamics?

A

heat cannot be changed completely into work in a cyclical process

entropy in an isolated system can never decrease

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18
Q

What is the third law of thermodynamics?

A

pure crystalline substances at absolute zero have an entropy of zero

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19
Q

What is the zeroth law of thermodynamics?

A

everything tends to move toward thermal equilibrium with everything else. (2 objects in thermal equilibrium = same temperature)

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20
Q

What is the definition for temperature?

A

the average kinetic energy of molecules

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21
Q

What equation shows the direct relationship between temperature and kinetic energy?

A

KE = 3/2kBT (where kB is Boltzmann’s constant)

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22
Q

How to convert celcius to Kelvin

A

add 273.15 to celcius

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23
Q

What is enthalpy?

A

the energy contained within chemical bonds

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24
Q

What is standard state?

A

a set of specific conditions as the reference point for measuring and reporting enthalpy, entropy, and Gibbs free energy

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25
Q

How to calculate ΔHRXN Using Bond Energies

A

add up the bond energies of all of the products and reactants. If a bond is broken during the reaction, energy is required, so the bond energy should be given a positive sign. If a bond is formed, energy is released, so the bond energy should be given a negative sign. Once again, multiply all bond energy values by their coefficients in the balanced equation.

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26
Q

ΔHcombustion

A

A high heat of combustion is associated with an unstable molecule and a low heat of combustion with a stable molecule.

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27
Q

ΔHformation

A

The enthalpy value for the formation of a compound from its elements in their standard states. If the number is negative, formation is an exothermic process, if it is positive, the process is endothermic.

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28
Q

ΔHsolution

A

The enthalpy value associated with the dissolution of a species into solution. We’ll discuss this in more detail when we cover solution chemistry.

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29
Q

ΔHvaporization

A

The enthalpy value associated with the phase change from liquid to gas. The reverse process (condensation) simply interchanges products and reactants and thus the sign is just changed.

30
Q

ΔHfusion

A

The enthalpy value associated with the phase change from liquid to solid. The sign changes for the reverse process (melting)

31
Q

What is entropy?

A

a measure of randomness or disorder in a system

32
Q

Entropy increases with 5 factors increasing?

A

number of items, volume, temperature, disorder, complexity

33
Q

What is gibb’s free energy?

A

∆G = the amount of “free” or “useful” energy available to do work

34
Q

What does isobaric mean?

A

constant pressure

35
Q

What does isothermal mean?

A

no heat exchange

36
Q

What is the fundamental thermodynamic relation?

A

∆G = ∆H - T∆S

37
Q

If ∆H is positive and entropy change is negative, what will the sign of ∆G be?

A

positive

38
Q

If the change in entropy is positive, and enthalpy is negative, the reaction is :

A

spontaneous

39
Q

If a reactant is dissolved in a solution, causing the temp to increase, the ΔG for this reaction is __

A

negative

40
Q

What equation relates Gibbs free energy to equilibrium?

A

∆G° = - RTlnKeq

Keq = e^ -ΔG/RT

41
Q

Arrhenius acid/ base definition

A

acids- produce H+ ions in solution

base- produce OH- ions in solution

42
Q

Bronsted Lowry acids/bases

A

acids - donate protons

bases - accept protons

43
Q

Lewis acid/bases

A

acid - accept pair of electrons

base- donate pair of electrons

44
Q

What is the definition of amphoteric ?

A

substances can act as either an acid or base

eg H2O

45
Q

Calculate pH with H+ concentration

A

pH= -log (H+)

46
Q

What is the equation for Kw?

A

Kw=[H3O+][OH-]=10^ -14

47
Q

Formula for acid dissociation constant

A

Ka = [H+][A-]/[HA]

48
Q

If Ka is greater than one, that means the acid is __

A

strong

49
Q

What is the formula for base dissociation?

A

Kb = [OH-][HA]/[A-]

50
Q

Smaller Kb indicates that an acid is __

A

strong

51
Q

Addition of either an acid or base to water shifts the equilibrium for the ionization of water to which direction?

A

left

52
Q

How to calculate the pH for weak acids

A
  1. write out balanced eq
  2. ICE table
  3. solve for x
  4. -log(H+)
53
Q

all strong acids and bases dissociate __ percent in water

A

100

54
Q

What are the strong acids?

A

HI, HBr, HCl, HNO3, HClO4, HClO3, H2SO4, h3O+

55
Q

What are the strong bases?

A

Group 1A hydroxides, NH2-, H-, Ca(OH)2, Sr(OH)2, Ba(OH)2, Na2O, CaO

56
Q

If an acid has a Ka less than 1, than it is __

A

weak

57
Q

If a base has a Kb less than one, it is a ___ base

A

weak

58
Q

What does the “salt of a weak acid” refer to?

A

conjugate base of the weak acid combined with a cation

59
Q

What does the “salt of a weak base” refer to?

A

conjugate acid combined with an anion to form a salt

60
Q

What does the term “equivalent” mean when it comes to titration?

A

the amount of acid or base necessary to produce or consume one mole of [H+] ions

61
Q

On a titration curve, what is one the x-axis and what is on the y-axis?

A

x-axis - volume of titrant

y-axis - pH

62
Q

What is the difference between an analyte and a titrant?

A

analyte - in beaker

titrate - added dropwise

63
Q

For SA and SB, at the equivalence point, ____

A

[H+] = [OH-]

64
Q

At the equivalent point/stoichiometric point, the [titrant]= __

A

[analyte]

65
Q

What is the pH of the equivalent points for WB w SA, WA w SB, SA w SB, WA w WB?

A

For WB w/ SA: pH < 7
For WA w/ SB: pH > 7
For SA w/ SB: pH about 7
For WB w/ WA: pH about 7

66
Q

half equivalence point = ____ on graph

A

midpoint of nearly horizontal section

67
Q

at half equivalence point, [HA] ___

A

[HA] = [A-]

68
Q

What are indicators?

A

weak acids that change color as they dissociate. To set up a titration, you should know the approx. pH of equivalence point to select an indicator that will change color at that pH

69
Q

Difference between the end point and equivalence point?

A

end point - when indicator causes color change

equivalent - when [titrant] = [analyte]

70
Q

Where is the buffer region?

A

nearly horizontal area surrounding the half-equivalence point

71
Q

What is the Henderson -Hasselbalch equation?

A

pH = pKa + log[A-]/[HA]

mcat (15 decks)

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