Quiz 3 Flashcards
1st law of thermodynamics
Conservation of energy. It states that energy cannot be created or destroyed, only transformed or transferred. The total energy of an isolated system remains constant
2nd law of thermodynamics
- The energy in the form of heat or work can’t be extracted from a
system unless there is a lower temperature heat reservoir available - Entropy tends to increase in an isolated system, meaning that energy transformations are not 100% efficient.
entropy change of reversible thermodynamic processes is always 0, explain
A reversible process is a process where the system can be returned to its initial state by infinitesimally reversing the changes made, meaning there is no net increase in entropy.
the entropy change of irreversible thermodynamic processes is always positive, explain
total entropy of an isolated system tend to increase, and for an irreversible process, the entropy always increases, resulting in a positive entropy change.
The 3rd law of thermodynamics
The Third Law of Thermodynamics states that as the temperature of a system approaches absolute zero (0 K), the entropy of a perfect crystalline substance approaches zero. So crystalline matters are imperfect which means they can
have some entropy even at absolute zero temperature
Thermodynamics establishes relationship between heat and what kind of energy?
all other forms of energy
What is the most macroscopic property in pharmacy?
solubility
environment
everything else outside the system
system
is the part of the environment that is under study or observation
Why is heat is an extensive property while temperature is an intensive property.
Heat is an extensive property because the amount of heat energy in a system depends on the quantity of matter and the conditions (e.g., a larger mass can store more heat).
Temperature, on the other hand, is an intensive property because it doesn’t depend on the size or mass of the system. Whether you have a small cup of water or a large bucket, if both are at the same temperature, this property remains the same.
Intensive variables or properties
Does not depend on amount
ex. temperature, pressure, and density
Extensive variables or properties
Does depend on amount
ex. mass or # of moles, volume, conc, and energy
Adiabatic thermodynamic process
no energy (heat) transfer between system and environment. Temperature change as a result of work done
Isothermal thermodynamic process
energy (heat) transfer can happen between system and environment. Temperature remains constant
To maintain a constant temperature, heat must be added to or removed from the system to balance the work done by or on the system
Isobaric thermodynamic process
pressure remains constant, everything else changes (volume, energy, temp.)
Isochoric thermodynamic process
volume remains constant, everything else changes (pressurePositive Work, energy, temp.)
Negative Work
Work done by the system (energy leaving the system).
Compression of a Gas: In a process where a gas is compressed, the work done on the gas is negative because the surroundings are doing work on the gas.
Positive Work
Work done on the system (energy entering the system).
Expansion of a Gas: In a thermodynamic process where a gas expands, doing work on the environment (such as lifting a piston), the work done by the gas is positive.
Endothermic processes
absorbs heat e.g. melting of ice, evaporation or
vaporization of water
Exothermic processes
produces heat e.g. freezing of water, combustion, etc
Heat Capacity (extensive property):
Ratio of amount of heat absorbed or released and change in temperature of a system without undergoing phase transition
Specific heat capacity
when amount is 1 g
Molar heat capacity
when amount is 1 mole
Latent heat
Heat needed to change phase happening at constant temperature and
pressure.
A gas expands by 0.25 liter against a constant pressure of 1.5 atm at 25C. What is the work in joules done by the system?
W = Volume * Pressure
0.987 atm = 10^6 dynes/cm^-2 and 0.25 L = 250 cm^3
Therefore, W = 1.519 atm x 10^6 dynes/cm2 x 250 cm3 = 0.38 x 10^9 dynes/cm
So 0.38 x 10^9 dynes/cm = 0.38 x 10^9 ergs = 38.0 joules because 1 joule = 107 ergs
What is the entropy change accompanying the vaporization of 2 moles of water in
equilibrium with its vapor at 25oC? (Heat of vaporization required to convert
water to its vapor = 10,500 cals/mole).
Entropy Change = Molar heat of Vaporization / Temperature
(10 ,500 cals/mole * 2 mole) / 298.15K = 70.67cals/K
Calculate the molar heat capacity if 4000 calories of heat are required to raise the
temperature from 30 to 35oC of 4 moles a liquid.
Cm (molar heat capacity) = Q / n (delta T)
then, 4000cal / 4mol (35-30 = 5C)
so 4000cal / 4 mol * 5C = 200cal/mol*C
when should Helmholtz free energy equation be used? ∆A = ∆E – T (∆S)
use to describe changes in state at constant temperature and volume, not constant pressure
when should Gibbs free energy equation be used? ∆G = ∆H – T (∆S)
use to describe changes in state at constant temperature and pressure, not constant volume
when should van’t Hoff equation be used
provides equilibrium constant at another temperature if it is known at one temperature
∆H and ∆S for the following reaction are 28.05 kJ and 108.7 J/K respectively.
NH4NO3(s) + H2O (l) –> NH4+ (aq) + NO3-(aq)
Calculate the value of ∆G0 for this reaction at 25C and explain why this reaction will be spontaneous.
∆G = ∆H – T (∆S) = 28050 J – (25+273.15K) x 108.7 J/K = -4.36 J, so spontaneous because of negative ∆G value
The concentration of urea in plasma and urine are 0.006 M and 0.345 M,
respectively. Calculate the free energy in transporting 0.01 mole of urea from plasma to urine. Is this transport process spontaneous, i.e., would it happen on its own? How many ATP molecules would be consumed in providing energy for this transport process?
ΔG = nRT ln(c2/c1)
N = 0.01 moles
R= 1.987 cal/moleK
T = 37 (body temp) +273.15 = 310.15 K
c2 = 0.345
c1 = 0.006
ΔG = (0.01 moles)(1.987 cal/moleK)(310.15 K) = 24.69 calories
The hydrolysis of 1 mole ATP releases 7.3 kCal (7300 calories).
So 24.69 calories * 6.0221x10^23 molecules of ATP / 7300 calories = 2.06x10^21 molecules of ATP
