BMB 428 final exam

Open system

Open system

Mass, heat and work can be exchanged with the surroundings

Closed System

matter not exchanged

Adiabatic system

Only work and energy can be exchanged with the surroundings (Δq = 0)

Isolated system

Nothing is exchanged with the surroundings (no heat, work, energy or matter)

Which of the following is an extensive property?

• specific heat capacity

• pressure

• temperature

• energy

energy

Isothermal

ΔT = 0

Reversible rxn

A system is at or near equilibrium (Pext = Pint)

Irreversible Rxn

System is not at equilibrium, occurs spontaneously (Pint does not equal Pext)

Extensive property and examples

depends on the amount of matter (ex: volume, heat capacity, gibbs free energy, enthalpy (H), mass, entropy (S)

Intensive Property and examples

does not depend on the amount of matter (ex: temperature, pressure, specific heat capacity, density)

Ideal gas law

PV = nRT

1st law of thermodynamics and accompanying equations

Energy cannot be created or destroyed, only converted

• du = dq + dw

• Euniverse = Esystem + Esurroundings = 0

2nd law of thermodynamics. and accompanying equations

Entropy of an irreversible process increases and the entropy of a reversible process remains unchanged

• ΔSuniverse > 0 (irreversible rxn)

• ΔSuniverse = 0 (reversible rxn)

• ΔSuniverse = ΔSsystem + ΔSsurroundings >/= 0

Heat is a property (T/F)

False

Which is FALSE?

• A diatomic ideal gas has three degrees of translational freedom

• A diatomic ideal gas has three degrees of rotational freedom

• A diatomic ideal gas has two degrees of vibrational freedom

• None of the above

A diatomic ideal gas has three degrees of rotational freedom.

• it has 2 degrees of rotational freedom

• 3 of translational

• 2 of vibrational

• overall 7

Units of heat capacity

J/K

ΔH = Δq at…

constant pressure

A gas in a piston (the system) is expanded reversibly in an isothermal process. Which of the following is true?

• heat is absorbed by the gas from the surroundings

• heat is neither absorbed nor given off by the gas to the surroundings

• heat is given off by the gas to the surroundings

• cannot tell

Heat is absorbed by the gas from the surroundings

3rd law of thermodynamics and accompanying equations

Every substance has a finite positive entropy, but at the absolute zero of temperature, the entropy may be zero, and it does in the case of a pure, crystalline substance

• LimS = 0 (as T—> 0K)

From the perspective of the universe, what is the criteria for a spontaneous process?

ΔSuniverse > 0 (spontaneous = irreversible)

A state function is…

a property

When ice melts (a phase transition)…

heat is absorbed and the temp of the water vapor stays the same

For the irreversible expansion of a diatomic ideal gas at constant temperature…

• the enthalpy decreases

• the enthalpy is unchanged

• the enthalpy increases

• the entropy is unchanged

enthalpy is unchanged

What is the sign for heat being absorbed?

Δq (system) = +

The heat capacity of a diatomic ideal gas at constant pressure is:

9/2 nR

Cp = Cv + nR

Cv = 7/2 nR + nR = 9/2 nR

Boyle’s Law

P = 1/V

PV = constant

P1V1 = P2V2 at constant Temp

Charle’s Law

P = T at constant n and V so, P1/T1 = P2/T2

Dalton’s Law

Ptotal = sum of Pis

What is Euler’s criteria and what does it do?

Proves if something is a property

Equation for Enthalpy (H)

H = U + PV

Equation for du

du = dq + dw

du = TdS-PdV

Equation for G

G = H-TS

Equationn for A (Helmholtz free energy)

A = U = -TS

What is heat (q)

Thermal energy transferred between systems due to a temperature difference

What are the state functions?

• Internal energy (E)

• Entropy (S)

• Enthalpy (H)

• Pressure (P)

• Volume (V)

• Temperature (T)

What are not state functions?

• heat (q) and work (w)

Equation for heat with specific heat in it

q = msΔT

s= specific heat

Heat capacity

• specific heat capacity

• molar heat capacity

Amount of heat that can be held

• specific heat = one gram, Cs

• molar heat = one mole, Cm

Equation for Cs (specific heat capacity)

Cs = q / mΔT

Equations for heat capacity (for monoatomic ideal gas) at:

• constant volume (Cv)

• constant pressure (Cp)

Cv = dU/dT = 3/2 nR

Cp = dH/dT = 5/2 nR

Equations for heat capacity (for diatomic ideal gas) at:

• constant volume (Cv)

• constant pressure (Cp)

Cv = 7/2*nR

Cp = 9/2*nR

Why is du = dq at constant volume

because dw = 0

dw = -Pext * dV

V = volume

dV = 0 so dW = 0

dw equation

dw = -Pext*dV

V = volume

Pext = external pressure

w = work

d= change

What is the SI unit for pressure?

atm

Pint equation (pressure internal)

P = nRT/V

SI unit for temperature

Kelvin (K)

Internal energy sign

U

Internal energy equation for monoatomic ideal gas and diatomic ideal gas

monoatomic: U = 3/2nRT

diatomic: 7/2nRT

For a reaction that is reversible or irreversible the value for U is ____

the same

What is entropy

disorder (S)

Equation for entropy (ΔS)

ΔS = dqrev/T

qrev = reversible heat

ΔS equation with Boltzmann constant in it

ΔS = Kb*ln*Ω

Kb = boltzmann constant (R/Na)

Ω = # of microstates

Definition of heat capacity at constant volume

T/F : the solute is the solid component of a solution

False

T/F: the molarity of a 0.0012 molal aqueous solution is about 1.2mM

True

T/F: The total concentration of reactants and products is constant for a chemical reaction

False

T/F: The more stable species in a mixture has a greater chemical potential

False

T/F: The rise of a protein α-helix is 3.6 angstrom

False

What is the pitch of the alpha helix of DNA

5.4 angstroms

What is the Rise of an alpha helix in DNA

1.5 angstroms

What is the # of residues per turn in DNA alpha helix

3.6 residues

how do you calculate pitch?

(# residues per turn)x Rise

Molality

moles solute / kg solvent

What is the equation describing Raoult’s Law for the solution containing solute A and solvent B

• Pa = Xa*Pa*

• Pa = Xb*Pa*

• Pa = Xa*Pb*

• Pa = Xa*Ka

• Pa = Xa*Pa*

Equation for Henry’s Law for the solution containing solute A and solvent B is:

• Pa = XaPa*

• Pa = XaPb*

• Pa = XaKa

• Pa=XaKb

Pa = XaKa

Raoult’s Law applies to:

• ideal solutions

• non-ideal solutions

• dilute non ideal solutions

• none of the above

ideal solutions

Henry’s Law applies to:

• ideal solutions

• non-ideal solutions

• dilute non-ideal solutions

• none

dilute non-ideal solutions

What is the entropic contribution to the Gibbs free energy of a process?

-TΔS

The entropy of mixing two liquids is:

• always +

• always -

• is ± depending on the nature of the liquids

• is ± depending on the temperature when mixed

always +

The chemical potential of an aqueous dilution of ethanol is:

• less than pure ethanol

• the same as pure ethanol

• greater than pure ethanol

• less or greater than pure ethanol depending on temperature

less than pure ethanol

The equilibrium constant for a gas chemical reaction calculated using molarity units and the equilibrium constant for the same reaction calculated using pressure units is…

same or different depending on the stoichiometry of the reaction

Liquid N boils at a very low temp because…

the dispersion interactions between nitrogen molecules are weak

What is G at equilibrium?

ΔG = 0

At equilibrium

• Keq < 1

• Keq = 1

• Keq > 1

• insufficient info to tell

insufficient info to tell

Which is not a van der Waals interaction:

• dipole-dipole

• ion-induced dipole

• dipole-induced dipole

• london interactions

ion-induced dipole

How do you find what the annealing temperature should be for PCR?

Tm - 5°C

What is the dielectric constant of water?

80

The boiling point of a solution will be…

• lower than BP of pure solvent

• equal to BP of pure solvent

• higher than BP of pure solvent

• lower or higher depending on nature of solute and solvent

higher than BP of pure solvent (bc of boiling point elevation)

Alaskan wood frogs can survive -40°C temps because of the following colligative property

freezing point depression

Hydrophobic interactions are the consequence of which law of thermodynamics

2nd