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CHEM 203 > PPT 3 > Flashcards

PPT 3 Flashcards

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1
Q

What is calorimetry?

A

study of heat released or absorbed during a physical/chemical process

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2
Q

Can heat capacity be used for calorimetry?

A

no, it is for a molecule

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3
Q

What type of calorimeter is a bomb calorimeter?

A

adiabatic (no net heat lost)

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4
Q

What is a bomb calorimeter?

A

constant volume container (bomb) immersed in a stirred water bath

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5
Q

How does a bomb calorimeter work?

A

immersed in an outer water bath, temperature of outer bath is adjusted to match temperature of calorimeter

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6
Q

What type of reactions are bomb calorimeters usually used for?

A

combustion reactions

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7
Q

What is an isobaric calorimeter?

A

reaction carried out in a thermally insulated vessel open to the atmosphere, done under constant pressure

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8
Q

How is the heat released in an isobaric calorimeter measured?

A

by calculating delta T

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9
Q

Which calorimteres can be used to measure calcoric value?

A

bomb and isobaric calorimeter

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10
Q

What is a calorie?

A

how much energy can food supply

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11
Q

What are the sample and reference of a differential scanning calorimeter?

A

there is a sample (the reaction/sample of interest) and a reference (does not undergo any physical/chemical change)

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12
Q

What is the differential?

A

difference between the behaviour of the sample abd tat if the reference material

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13
Q

What is the experimental setup of the differential scanning calorimeter?

A

two identical compartments are heated electrically at a constant rate (same energy in each), one containing the reference and one containing the sample

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14
Q

What is needed to maintain the compartments at equal temperature for a differential scanning calorimeter?

A

power

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15
Q

Which part of the differential scanning calorimeter requires more power?

A

the sample

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16
Q

When would power not cause the same rise in T of the sample of interest?

A

when the sample undergoes a physical/chemical change

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17
Q

What happens if the change in the sample is endothermic?

A

more energy will have to be supplied to maintain the temperature

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18
Q

What happens if there is excess power in the sample?

A

gives us excess heat (change in enthalpy)

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19
Q

What is a thermogram?

A

a plot of Pext against temperature

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20
Q

When is DSC used?

A

to study the effects of change in temperature on the folded structure of biological molecules (folded state to the denatured state) and determine the melting temperature

determines effects of mutations/pH and other conditions on the structure of the biological membrane

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21
Q

What is melting temperature?

A

the temperature at which folded and unfolded states are equally populated

22
Q

How is DSC used in pharmaceutical studies?

A

identified a synthetic compund BRD4592 that targets Myobacterium tuberculosis by inhibiting trytophan synthase (TrpAB) enzyme

determined which interface the inhibitor binds to: BRD4592 binds to TrpAB alpha-beta-subunit interface

they were able to determine how compound actually binds

23
Q

What is an isothermal titration calorimeter?

A

a differential technique comparing a sample to a reference, both vessels at the same temprature, precisely determined small volumes of reagent added to a sample vessel

24
Q

What is the measurement of an ITC?

A

power required to keep the temperature of the sample and reference vessels the same

25
Q

What can ITC be used for? give an example

A

used to gain insights into mechanism of binding

ex: enzyme/substrate
start with protein and slowly add ligand of interest (in a water bath), calculate molar ratio, know how much protein, ligand and macromolecule you have

26
Q

What is an exothermic ITC?

A

less power needed

27
Q

What is an endothermic ITC?

A

more power needed

28
Q

What did the nobel prize winners for ITC discover?

A

understood how enzymes bind (dimer), allosteric binding, still didnt know if binding happened at once or was step wise

29
Q

How is overall enthalpy calculated?

A

The sum of the enthalpy for individual steps

30
Q

How is the standard state of gases defined?

A

pure substance at 1 barr

31
Q

How is the standard state of solutions defined?

A

molar concentration (1 mol/L)

32
Q

What does the symbol º indicate?

A

designates standard state

33
Q

What is necessary to drive molecules apart/for a phase change?

A

energy

34
Q

What is the standard enthalpy of vaporization?

A

the energy supplied as heat at constant pressure per mole of molecules that are vaporized under standard consitions

35
Q

What is freezing?

A

liquid to solid

36
Q

What is fusion?

A

solid to liquid

37
Q

What is sublimation?

A

solid to gas

38
Q

What is deposition?

A

gas to solid

39
Q

What is condensation?

A

gas to liquid

40
Q

What is vaporization?

A

liquid to gas

41
Q

Is delta H an intensive or extensive property? Why?

A

extensive, depends on the amount of reactants consumed

42
Q

What is a liposome?

A

absorbs a significant amount of heat at a temperature characteristic of the phospholipid which compose the liposome

43
Q

How can liposome be measured?

A

using DSC

44
Q

What is the difference between gel and liquid phase of acyl chain?

A

more tightly packed in gel phase and less tightly packed in liquid crystalline phase

45
Q

What is bond enthalpy?

A

the corresponding standard molar enthalpy

46
Q

How can we get a positive bond association energy?

A

by breaking the bond

47
Q

What happens as molecules get closer together?

A

they stabilize

48
Q

Why dont single atoms have a delta H formation?

A

they are already in their elemental state

49
Q

What is the relationship between enthalpy and tmerature?

A

proportional

50
Q

Is molar enthalpy an intensive or extensive property?

A

intensive

51
Q

What is true about delta H fusion and delta H freezing?

A

they have the same value but opposite signs

CHEM 203 (4 decks)

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