Ch. 4 Equilibrium and Thermodynamics Flashcards
What is reversibility?
reactants are converted into products at the same time products are converted into reactants
IN a chemical reaction, the reaction rate is dependant upon?
reactant concentration.
The more product produced, the higher the decomposition rate
What is the rate equation of equilibrium?
Rate(forward) = Rate(reverse)
A reaction that is Spontaneous favors which direction?
Forward direction, making product
A reaction that is non-spontaneous favors which direction?
The reverse direction, to reactants
At equilibrium, what is ΔG
0
Keq is used to determine equilibrium constant, which is denoted as
products/reactants (coefficients are raised as powers)
When Keq favors the products
it will be a large value
Numerator greater than denominator
When Keq favors the reactants
It will be a smaller value
Denomenator larger than numerator
Which phases should not be included in the equilibrium expression?
Solids and pure liquids (water)
How would you calculate Keq for a reverse reaction?
this is the reciprocal of Keq, so 1/Keq
What are the units for Keq
moles/liter (Molarity)
Keq is negative when reactants are favored (T/F)
False.
Keq should never be negative
What is the reaction quotient?
A formula used to determine if a reaction is at equilibrium
It is also used to predict the direction in which the reaction will take to reach equilibrium
When Q < Keq
Ratio of products to reactants is lower than at equilibrium, products will want to form.
When Q >Keq
Raio of products to reactants is higher than t equilibrium, reactants will want to form.
When Q = Keq = 1
Equilibrium is reached
Calorimetry mimics which type of reaction?
combustion
1 calorie = how many Joules?
4.184
What is a calorie?
The amount of heat needed to raise the temperature of 1 gram of water by 1 degree Celcius (1cal/g°C)
What is the specific heat capacity of water in Joules and calories
4.184 J/g °C
1 cal/g °C
1 mL of water = how many grams?
1 gram
What is heat capacity?
The heat required to raise the temperature of a system by 1 °C
What is ΔH?
Enthalpy change (unit is kJ/mol)
What is Enthalpy?
Heat absorbed/released by the system (heat transfer)
Under what conditions would ΔH be negative?
Energy is released
Energy is produced
Heat is released
Heat is produced
Under what conditions would ΔH be positive?
Energy is absorbed
Heat is absorbed
Enthalpy(H) may also be used with the internal energy of a system. What is the formula?
ΔU = Q-W (or ΔU= Q+PΔV) Q= heat transfer W = work done by the system (PV)
What is an endothermic process?
One that requires heat to work (ΔH positive)
What does it mean if something has low entropy?
It has concentrated energy
What does it mean if something has High entropy?
energy is spread out among the molecule
Which entropy would be a favorable process?
Spontaneous, when ΔS is positive
What unit is used for Entropy(S)?
J/K or J/K mol
What is the formula for standard entropy(ΔS°)?
Products - reactants
The Gibbs free energy formula is
ΔG = ΔH - TΔS
What is Gibbs free energy?
The maximum amount of work that can be performed by a system consisting of one or more reversible reactions.
This allows us to know if a reaction is spontaneous
What type of reaction is ΔH > 0?
Endothermic, heat needs to be added to the system
What type of reaction is ΔH < 0?
Exothermic, heat is removed from the system
What is ΔHf
Standard Enthalpy of formation (standard heat of formation), the enthalpy change associated with forming one mole of a compound from its elements under standard conditions (1 atm, 25°C)
Enthalpy of any element in its elemental form is
0
What is the formula for Bond dissociation?
ΔHrxn = ΔH°bonds broken - ΔH°bonds formed
Forming bonds is what type of reaction
Exothermic, bonded atoms are more stable and lower in energy
If ΔHrxn > 0 it is
Endothermic, energy is required
For a reaction to take place it must overcome
Activation energy
If ΔG < 0 during a reaction
it is spontaneous and exergonic
If products are higher than reactants, energy must be absorbed to form products, how does this relate to ΔG?
non-spontaneous, ΔG is a positive and endergonic reaction
What is the difference between Kinetic energy and Thermodynamics?
Kinetics focuses on the rate
Thermodynamics is about stability, spontaneity, and equilibrium
Keq and ΔG have a _________ relationship
inverse
