Thermodynamics

Question 1

State of a system

Answer 1

Values of all relevant macroscopic properties - composition, energy, volume, temperature, pressure

Question 2

State functions

Answer 2

Determined by state of system, not how it got there (E, P, T, V)

Question 3

Enthalpy

Answer 3

H = U + PV

Question 4

Why is enthalpy a state function?

Answer 4

U, P, and V are state functions

Question 5

What is true about the change in enthalpy for a constant-pressure process?

Answer 5

Change in enthalpy equals heat change at constant pressure

Question 6

What does ∆H refer to?

Answer 6

Refers to all the reacting species in molar quantities

Question 7

Specific heat (s)

Answer 7

Heat to raise temperature of one gram of substance by one degree celsius

Question 8

Heat capacity (C)

Answer 8

Heat to raise temperature of a given quantity of substance by one degree celsius

Question 9

Relationship between specific heat and heat capacity

Answer 9

s is an intensive property
C is an extensive property
C = ms

Question 10

Standard enthalpy of formation of an element in its most stable form

Answer 10

zero

Question 11

Standard enthalpy of formation (ΔHf°)

Answer 11

Reference point for all enthalpy expressions

Question 12

Standard enthalpy of formation of a compound

Answer 12

Heat change that results when 1 mole of the compound is formed from its elements at a pressure of 1 atm

Question 13

Standard enthalpy of a reaction

Answer 13

Enthalpy of a reaction carried out at 1 atm
ΔHºrxn = ΣnΔHºf(products) - ΣmΔHºf(reactants)

Question 14

Hess’s law

Answer 14

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

Question 15

Heat of solution / enthalpy of solution

Answer 15

Heat generated or absorbed when a certain amount of solute dissolves in a certain amount of solvent
ΔHsln = Hsln - Hcmp

Question 18

Enthalpy/heat of vaporization

Answer 18

Heat a liquid takes from its surroundings to replace the energy taken by the vaporizing molecules in order to keep the temperature constant