2.2 reaction feasibility Flashcards
what is the standard enthalpy of formation
the enthalpy change when one mole of a substance is formed from its elements in their standard states
what is the standard state of a substance
the most stable state at a pressure of 1 atmosphere and at a specified temperature, usually taken as 298K
how can the standard enthalpy of a reaction be calculated
- from the standard enthalpies of formation of the reactants and products
- products - reactants
what is meant by the entropy of a system
a measure of the degree of disorder of the system
what is the symbol for entropy
S
true or false: the greater the degree of disorder, the lower the entropy
false
true or false: the greater the degree of disorder, the greater the entropy
true
do solids have high or low disorder
low
do gases have high or low disorder
high
does entropy increase or decrease as temperature increases
increase
is there a rapid or a slow increase in entropy at the melting point of a substance
rapid
is the increase in entropy more rapid and larger at the melting point or the boiling point of a substance
boiling point
what does the second law of thermodynamics state
the total entropy of a reaction system and its surroundings always increases for a spontaneous process
does the heat energy released by a reaction system into the surroundings increase or decrease the entropy of the surroundings
increase
does the heat energy absorbed by the reaction system from the surroundings decrease or increase the entropy of the surroundings
decrease
what does the third law of thermodynamics state
the entropy of a perfect crystal at 0K is zero
what is the standard entropy of a substance
the entropy value for the substance in its standard state
how can the change in standard entropy for a reaction system be calculated
from the standard entropies of the reactants and products
when is a reaction said to be feasible
when the change in free energy between reactants and products is negaitive, and a reaction occurs
what is the change in free energy related to
enthalpy and entropy changes
what is a feasible reaction
one that tends toward the products rather than the reactants
does a reaction being feasible give an indication on the rate of the reaction
no
how can the standard free energy change be calculated
from the standard free energies of formation of the reactants and products
how can the feasibility of a reaction under standard conditions be predicted
from the calculated value of the change in standard free energy
how can the temperatures at which a reaction may be feasible be estimated
by considering the range of values of T for which the free energy is greater than zero
when is any reaction feasible
under non standard conditions, when the free energy value is negative
what does free energy equal at equilibirum
0
for how long will a reversible reaction proceed spontaneously
until the composition is reached, where free energy = 0.
