Gibbs Free Energy

Energy releasing reactions

- ∆ G

I Cal = ________ cal

1 Cal = 1000 cal

I cal = ________J

1 cal = 4.186 Joules

What is the specific heat of H20 (l)

1 cal/ (g) (K)

How much does water weigh in grams?

1g/mL

What are the standard conditions for Gibbs free energy problems?

25 degrees C (298K) 1 atm pressure 1 M concentrations

What is the opposite of sublimation?

Deposition. Transition from the gas phase to a solid, also skipping the liquid state.

Many reactions in our bodies are kinetically unfavorable, which means the Ea (activation energy) is high even when they are thermodynamically favorable. This is why our bodies have ____________ to lower the activation energy

ENZYMES!! Which catalyze reactions :)

first law of thermodynamics

Energy can be transferred and transformed, but it cannot be created or destroyed.

What part of the Gibbs Free Energy equation tells you if the reaction is exothermic or endothermic?

Enthalpy

ΔH represents

Enthalpy

What part of the Gibbs Free Energy equation tells you if the reaction is spontaneous or not?

Entropy

ΔS represents

Entropy

What is the goldfish mnemonic for the Gibbs free energy formula?

Goldfish ARE (equals sign) Horrible WITHOUT (minus sign) Tartar Sauce ΔG = H - ΔTS

Heat vs. Temperature

Heat is the amount of energy transferred due to a change in temperature Temperature is a measure of the kinetic energy of the particles in a system.

What units are ∆ G represented by?

Joules/mol of reactant

Energy required to melt ice to water

Latent heat of fusion

Closed system

No mass is exchanged, only energy is exchanged number of moles (n) stays constant

How would you find the equilibrium temperature for questions regarding Gibbs free energy?

PLUG IN ZERO FOR ΔG because at equilibrium ΔG = 0

Is heat (Q) a process function or a state function?

PROCESS FUNCTION Heat is the transfer of energy from one substance to another as a result of their differences in temperature. Objects are in thermal equilibrium only when their temperatures are equal. Heat is therefore a process function and not a state function; we can quantify how much thermal energy is transferred between two or more objects as a result of their difference in temperatures by measuring heat transferred.

Change in entropy equation

Q = heat that is gained/lost in REVERSIBLE process T = temp (K) entropy units: J/(mol*K)

When should you use Q=mL vs q = mcΔt?

Q = mL for PHASE CHANGES q = mcΔt for TEMPERATURE CHANGES

Gas-Liquid Equilibrium

Some liquid may have enough kinetic energy to vaporize into gas (an endothermic process). Each time the liquid loses a high-energy particle, the temperature of the remaining liquid decreases.

The amount energy required to raise the temperature of one gram of substance by one degree Celsius (or one kelvin) is called

Specific heat

Conversely what is STP?

Standard Temperature and Pressure (STP): 0 degrees C (273K) 1 atm Used for kinetics, equilibrium, and thermodynammics problems; STP is used for ideal gas calculations

A property of the system that changes independently of its pathway

State function

What is the phase change associated with the greatest increase in entropy?

Sublimation, a liquid becomes a much more disordered gas

True or false: enthalpy is a state function

TRUE! Enthalpy is a state function because the pathway taken to get to the final state of the system will not affect enthalpy

What are the 3 types of stress that can act on a system?

Temperature, pressure, concentration

What is the triple point vs critical point?

The triple point is where all three phase boundaries meet and exist in equilibrium The Critical point is the temperature and pressure above which there is no distinction between phases

One cup containing 100 grams of water at 300K is mixed into another cup containing 200g of water at 450K. What is the equilibrium temperature of the system? (Note: assume that the pressure is sufficiently high to avoid boiling) pg 227 gen chem

The two liquids undergo thermal exchange ; thus the heat given off by one liquid will equal the heat absorbed by the other. q cold = - q hot m cold C h20 Δ T cold = -m hot C h20 (-Δ T hot) (100g)(1g/kg/K)(x-300K)=-(200g)(1g/kg/K)(x-450K) 100x - 30,000 = -200x - 90,000 300x = 120,000 x = 120,000/300 x = 400 K

Delta G can be ____________ not measured. a) calculated b) derived c) synthesized

a) calculated! Delta G can be CALCULATED not measured.

Latent heat is a general term for _____________ What units is latent heat measured in? a) enthalpy b) entropy c) change in heat

a) enthalpy heat absorbed or radiated during a change of phase at a constant temperature and pressure UNITS: cal/g

When measuring enthalpies of the same reaction (forward and reverse), they have the same magnitude of energy but endothermic is a ___ value and exothermic is a ___ value a) positive/negative b) negative/positive

a) positive/negative endothermic reactions are positive because they release heat into the surroundings exothermic reactions are negative because they require the input of heat from the surroundings

Knowing that heat can transfer energy from a system to its surroundings is a key concept tested on ___________ questions. a) thermodynamic b) calorimetry c) heat transfer

b) calorimetry Remember that the cooler object gains thermal energy and the hotter object loses it. Set up equations as q cold = - q hot

SMALLER activation energy _____ reaction a) slower b) faster

b) faster the FASTER the reaction will occur!

__________________ is the average energy required to break a particular type of bond between atoms in the gas phase. Is this process endo or exothermic? a) breakage energy b) displacement energy c) bond enthalpies

c) bond enthalpies, also known as bond dissociation energy. This is an endothermic reaction because it takes energy to pull two atoms apart. The reverse process, bond formation, is generally exothermic.

Thermodynamics vs kinetics

delta G= thermodynamic, so it determines whether a reaction will occur kinetics is a measure of the rate at which a reaction will occur

What is the latent heat equation?

is a measure of the heat energy (Q) per mass (m) released or absorbed during a phase change. L is the latent heat Note there is no change in temperature used in this formula because there is no change in temperature, only a phase change

List the state functions

pressure (P), density (p), temperature (T), volume (V), enthalpy (H), entropy (S), internal energy (U), Gibbs free energy (G)

How is heat transfer represented?

q

Write out the equation for heat transfer

q = mcΔT m = mass c = specific heat of substance ΔT = the change in temperature in Celsius or kelvins)

The process when a solid goes directly into the gas phase

sublimation ex Dry ice (solid C02) sublimes at a room temperature and atmospheric pressure; the absence of the liquid phase makes it a convenient dry refrigerant

The temperature at which the vapor pressure of the liquid equals the ambient (also known as external, applied, or incident) pressure is called _____________

the boiling point

Hess's Law

when reactants are converted to products, the change in enthalpy is the same whether the reaction takes place in one step or in a series of steps

Match the following: Δ G = 0 Δ G = > 0 Δ G = < 0 a) spontaneous b) equilibrium c) non spontaneous

Δ G = 0 b) equilibrium Δ G = > 0 c) non spontaneous Δ G = < 0 a) spontaneous

second law of thermodynamics

Every energy transfer or transformation increases the entropy(disorder) of the universe.

True or False: because the products are thermodynamically more stable than reactants, the rate is high

FALSE. This is not true!! This statement is basically stating that thermodynamics are the same as kinetics and they are NOT!