chem - thermodynamics

Question 1

Specific heat capacity (C) is defined as: the amount of energy required to raise the temperature of ___ of a substance by ___

If a material has a high specific heat capacity, it requires (more/less) energy to raise its temperature

If a material has a low specific heat capacity, it requires (more/less) energy to raise its temperature

Answer 1

Specific heat capacity (C) is defined as the amount of energy required to raise the temperature of 1 g of a substance by 1 degree Celsius

If a material has a HIGH specific heat capacity, it requires MORE energy to raise its temperature

If a material has a LOW specific heat capacity, it requires LESS energy to raise its temperature

Question 2

What does each mean:

Isobaric

Isochoric

Adiabatic

Isothermal

Endothermic

Answer 2

Isobaric
An isobaric process is a type of thermodynamic process in which pressure remains constant. In this process, heat can enter or leave the system.

Isochoric
An isochoric process is a type of thermodynamic process that occurs at constant volume. In this process, heat can enter or leave the system.

Adiabatic
An adiabatic process is a type of thermodynamic process in which there is no heat exchange between the system and its surroundings.

Isothermal
An isothermal process is a type of thermodynamic process in which temperature remains constant. In this process, heat can enter or leave the system.

Endothermic
An endothermic process is a type of thermodynamic process in which the system absorbs heat from their surroundings, causing a decrease in temperature. This involves a transfer of heat into the system.

Question 3

First law of thermodynamics

Answer 3

energy cannot be created/destroyed
- applies to the universe, heat energy is transferred b/w the system & surroundings

Question 4

Second law of thermodynamics

Answer 4

entropy of the universe is always increasing
- therefore ALL spontaneous processes PRODUCE an INCREASE in entropy of the universe

Question 5

3rd law of thermodynamics

Answer 5

The entropy of a pure crystalline substance at absolute zero temperature (0K) is zero
- no motion/kinetic energy (no entropy)

Question 6

What is the effect of a catalyst on Gibbs free energy?

Answer 6

ΔG is not dependent on the presence of a catalyst and thus does not change in the presence of a catalyst. Catalysts do not change any thermodynamic properties of a reaction but only change the kinetic properties of how fast the reaction goes.

Question 7

What is endergonic vs endothermic?

Answer 7

Endergonic refers to the change in FREE ENERGY of the system while

endoTHermic refers to the change in ENTHALPY of the system. Thus, they are not interchangeable terms.

Question 8

In an exergonic reaction where the ΔG is negative, the equilibrium constant Keq > 1, meaning the _____________ are favored at equilibrium.

reactants or products?

Answer 8

PRODUCTS

Question 9

Endergonic reactions have a positive or negative ΔG?

Answer 9

POSITIVE

Endergonic reactions absorb free energy from the surroundings and are considered non-spontaneous reactions with a positive ΔG.

On the other hand: Exergonic reaction, a spontaneous reaction with a negative ΔG, releases free energy to the surroundings.

Question 10

Kinetics vs thermodynamics

Answer 10

Kinetics describes the rate at which a reaction happens, focusing on how fast a reaction happens without depending on the spontaneity, or the direction of the reaction. (RATE)

Thermodynamics describes the energetics of the reaction, focusing on the direction or the spontaneity of the reaction without depending on the speed of the reaction. (ENERGIES)

Question 11

The highest point in a reaction coordinate diagram is representative of which of the following?

A.
The reaction intermediate

B.
The reactants of an endergonic reaction

C.
The products of an endergonic reaction

D.
The transition state

E.
The ΔG of the reaction

Answer 11

D.
The transition state

Transition states – the highest energy points on the reaction coordinate diagram. The greater the transition state height, the greater the activation energy.

Intermediates – substances formed during the reaction but are not part of the overall reactants or products. They are usually products in the first reaction step, which are immediately consumed in the second reaction step.

Question 12

The rate-determining step, or the slow step, is the step with the _______ activation energy in a chemical reaction.

highest/lowest/middle

Answer 12

HIGHEST

• this is the largest energy barrier the rxn has to overcome