U1: Topic 6 Reaction Feasibility Flashcards
What is the standard enthalpy of formation?
Enthalpy change when 1 mole of a substance is formed from its elements in their standard states.
The standard state of a substance is its?
Most stable state at a pressure of 1 atmosphere and at a specified temperature usually taken as 298 K.
0 degrees celsius is what kelvin?
273K
The enthalpy of formation of elements is?
0
The entropy is given by symbol S. What does it mean?
Measure of the degree of disorder of the system.
The greater the degree of disorder the …..?
Greater the entropy.
Solids have …. disorder and gases have ….. disorder?
low
high
Entropy in increases as Temperature ….?
Increases
Rapid increase in entropy at ………… of substance and even more rapid and larger entropy change at the ……..?
Melting point
Boiling point
What is the second law of thermodynamics?
The total entropy of a reaction system and its surroundings always increases for a spontaneous process.
Heat energy released by the reaction system into surroundings increases what?
Entropy of surroundings .
Heat energy absorbed by the reaction system from the surroundings does what?
Decreases the entropy of the surroundings.
What does the third law of thermodynamics state?
Entropy of a perfect crystal at 0 K is zero.
The standard entropy of a substance is the what?
Entropy value for the substance in its standard state.
Entropy is increased by dissolving how?
The solid particles spread through the solvent and become less ordered/ more disordered.
If the change in free energy 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. Does not give any indication of rate of reaction.
For a reaction to be spontaneous…..
Delta G must be negative.
The temperatures at which a reaction is feasible can be estimated by considering what?
Range of values of T for which delta G <0
Under non-standard conditions any reaction is feasible if?
Delta G is negative.
A reaction will proceed spontaneously until the composition is reached where?
Delta G=0
