Reaction feasability Flashcards
What is the standard enthalpy of formation 🔺H?
the enthalpy change when one mole if a substance id formed from its elements in their standard states
kJ mol-1
What is the standard state of a substance?
Its most stable state at a pressure of 1 atmosphere and at a specified temperature, usually taken as 298K
What is the entropy S of a system?
a measure of the degree of disorder of the system
The greater the degree of disorder, the greater the entropy
JK-1 mol-1
what degree of disorder to gases and solids have?
gases-high
solids-low
What happens to entropy as temperature increases?
entropy increases
Describe the entropy change at melting points and boiling points?
Rapid increase at melting point
even more rapid and larger change at 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
What does heat energy released into the surroundings by the reaction system do to the surroundings?
increases the entropy
What does heat energy absorbed by the reaction system from the surroundings do to the surroundings?
decreases the entropy
What does the third law of thermodynamics state?
the entropy of a perfect crystal at 0K is 0
What is the standard entropy of a substance?
the entropy value for a substance in its standard state
What if the change in free energy 🔺G between reactants and products is negative?
a reaction may occur and the reaction is said to be feasible
What is a feasible reaction?
one that tends towards the products rather than the reactants
What does the feasibility of a reaction not give an indication of?
the rate of the reaction
How can the temperatures at which a reaction may be feasible be estimated?
by considering the range of values of T for which 🔺G<0
