REACTION FEASABILITY Flashcards
Define the standard enthalpy of formation.
Enthalpy change when one mole of a substance is formed from its elements in their standard states.
Describe the standard state of a substance.
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.
Explain how to calculate the standard enthalpy of a reaction.
The standard enthalpy of a reaction can be calculated using the formula: ∆H° = Σ∆H°f(products) - Σ∆H°f(reactants).
What does the entropy (S) of a system measure?
The entropy (S) of a system measures the degree of disorder of the system.
How does the degree of disorder relate to entropy?
The greater the degree of disorder in a system, the greater the entropy.
Compare the disorder levels of solids and gases.
Solids have low disorder and gases have high disorder.
Explain the relationship between temperature and entropy.
Entropy increases as temperature increases.
Describe the change in entropy at the melting point of a substance.
There is a rapid increase in entropy at the melting point of a substance.
What happens to entropy at the boiling point of a substance?
There is an even more rapid and larger change in entropy at the boiling point of a substance.
State the second law of thermodynamics.
Total entropy of a reaction system and its surroundings always increases for a spontaneous process.
Describe the effect of heat energy released by a reaction system on the surroundings.
increases the entropy of the surroundings.
Explain the impact of heat energy absorbed by a reaction system on the surroundings.
decreases the entropy of the surroundings.
Define the third law of thermodynamics.
The third law of thermodynamics states that the entropy of a perfect crystal at 0 K is zero.
What is the standard entropy of a substance?
The standard entropy of a substance is the entropy value for the substance in its standard state.
How can the change in standard entropy for a reaction system be calculated?
The change in standard entropy for a reaction system can be calculated from the standard entropies of the reactants and products using the formula: ΔS° = ΣS°(products) - ΣS°(reactants).
Explain the relationship between change in free energy, enthalpy, and entropy changes for a reaction.
The change in free energy for a reaction is related to the enthalpy and entropy changes by the equation: ΔG° = ΔH° - TΔS°.
What indicates that a reaction is feasible?
If the change in free energy (ΔG°) between reactants and products is negative, a reaction may occur and is said to be feasible.
Describe a feasible reaction in terms of reactants and products.
A feasible reaction is one that tends towards the products rather than the reactants.
Describe the relationship used to calculate the standard free energy change for a reaction.
The standard free energy change (∆G°) for a reaction can be calculated using the formula: ∆G° = Σ∆G°(products) - Σ∆G°(reactants).
Explain how the feasibility of a chemical reaction can be predicted.
The feasibility of a chemical reaction under standard conditions can be predicted from the calculated value of the change in standard free energy (∆G°). If ∆G° is negative, the reaction is feasible.
Define the condition for a reaction to be feasible under non-standard conditions.
Under non-standard conditions, any reaction is feasible if the change in free energy (∆G) is negative.
How can the temperatures at which a reaction may be feasible be estimated?
The temperatures at which a reaction may be feasible can be estimated by considering the range of values of T for which ∆G° is less than 0.
What occurs at equilibrium in terms of standard free energy change?
At equilibrium, the standard free energy change (∆G°) is equal to 0.
Describe the behavior of a reversible reaction in relation to standard free energy change.
A reversible reaction will proceed spontaneously until it reaches a composition where the standard free energy change (∆G°) is equal to 0.
