PPT 3

Question 1

What is calorimetry?

Answer 1

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

Question 2

Can heat capacity be used for calorimetry?

Answer 2

no, it is for a molecule

Question 3

What type of calorimeter is a bomb calorimeter?

Answer 3

adiabatic (no net heat lost)

Question 4

What is a bomb calorimeter?

Answer 4

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

Question 5

How does a bomb calorimeter work?

Answer 5

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

Question 6

What type of reactions are bomb calorimeters usually used for?

Answer 6

combustion reactions

Question 7

What is an isobaric calorimeter?

Answer 7

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

Question 8

How is the heat released in an isobaric calorimeter measured?

Answer 8

by calculating delta T

Question 9

Which calorimteres can be used to measure calcoric value?

Answer 9

bomb and isobaric calorimeter

Question 10

What is a calorie?

Answer 10

how much energy can food supply

Question 11

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

Answer 11

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

Question 12

What is the differential?

Answer 12

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

Question 13

What is the experimental setup of the differential scanning calorimeter?

Answer 13

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

Question 14

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

Answer 14

power

Question 15

Which part of the differential scanning calorimeter requires more power?

Answer 15

the sample

Question 16

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

Answer 16

when the sample undergoes a physical/chemical change

Question 17

What happens if the change in the sample is endothermic?

Answer 17

more energy will have to be supplied to maintain the temperature

Question 18

What happens if there is excess power in the sample?

Answer 18

gives us excess heat (change in enthalpy)

Question 19

What is a thermogram?

Answer 19

a plot of Pext against temperature

Question 20

When is DSC used?

Answer 20

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

Question 21

What is melting temperature?

Answer 21

the temperature at which folded and unfolded states are equally populated

Question 22

How is DSC used in pharmaceutical studies?

Answer 22

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

Question 23

What is an isothermal titration calorimeter?

Answer 23

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

Question 24

What is the measurement of an ITC?

Answer 24

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

Question 25

What can ITC be used for? give an example

Answer 25

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

Question 26

What is an exothermic ITC?

Answer 26

less power needed

Question 27

What is an endothermic ITC?

Answer 27

more power needed

Question 28

What did the nobel prize winners for ITC discover?

Answer 28

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

Question 29

How is overall enthalpy calculated?

Answer 29

The sum of the enthalpy for individual steps

Question 30

How is the standard state of gases defined?

Answer 30

pure substance at 1 barr

Question 31

How is the standard state of solutions defined?

Answer 31

molar concentration (1 mol/L)

Question 32

What does the symbol º indicate?

Answer 32

designates standard state

Question 33

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

Answer 33

energy

Question 34

What is the standard enthalpy of vaporization?

Answer 34

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

Question 35

What is freezing?

Answer 35

liquid to solid

Question 36

What is fusion?

Answer 36

solid to liquid

Question 37

What is sublimation?

Answer 37

solid to gas

Question 38

What is deposition?

Answer 38

gas to solid

Question 39

What is condensation?

Answer 39

gas to liquid

Question 40

What is vaporization?

Answer 40

liquid to gas

Question 41

Is delta H an intensive or extensive property? Why?

Answer 41

extensive, depends on the amount of reactants consumed

Question 42

What is a liposome?

Answer 42

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

Question 43

How can liposome be measured?

Answer 43

using DSC

Question 44

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

Answer 44

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

Question 45

What is bond enthalpy?

Answer 45

the corresponding standard molar enthalpy

Question 46

How can we get a positive bond association energy?

Answer 46

by breaking the bond

Question 47

What happens as molecules get closer together?

Answer 47

they stabilize

Question 48

Why dont single atoms have a delta H formation?

Answer 48

they are already in their elemental state

Question 49

What is the relationship between enthalpy and tmerature?

Answer 49

proportional

Question 50

Is molar enthalpy an intensive or extensive property?

Answer 50

intensive

Question 51

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

Answer 51

they have the same value but opposite signs