1) Which of the following describes the relationship between standard free energ
ID: 1041407 • Letter: 1
Question
1) Which of the following describes the relationship between standard free energy and spontaneity?
A-The more positive the value of ?G?, the more spontaneous the process.
B-The more negative the value of ?G?, the more spontaneous the process.
C-When the value of ?G? is zero, the reaction is spontaneous.
D-When the value of ?G? is equal to zero, the reaction is nonspontaneous.
2) A system is observed to spontaneously undergo a change. This change is accompanied by a decrease in the system’s entropy. Has the second law of thermodynamics been violated?
A-No, because the surroundings must have experienced an entropy decrease that is numerically greater than the entropy decrease experienced by the system.
B-No, because the surroundings must have experienced an entropy increase that is numerically greater than the entropy decrease experienced by the system.
C-No, because the surroundings must have experienced an entropy decrease that is numerically smaller than the entropy decrease experienced by the system.
D-No, because the surroundings must have experienced an entropy increase that is numerically smaller than the entropy decrease experienced by the system.
Suppose an ice cube melts in a cup of water. What is the direction of energy flow?
A-From the ice to the water
B-From the water to the ice
C-No net change in energy flow
D-it is impossible to tell.
Explanation / Answer
1. Ans: B- The more negative the value of G, the more spontaneous the process.
A Spontaneous process Is that process in which it releases free energy and hence deltaG must be negative.
In Mathematical Form, Gibbs Free Energy can be represented by-
deltaG=deltaH - T deltaS
When deltaH is negative and deltaS is positive, the sign of deltaG will be negative, (and temperature always positive as it is Kelvin Temperature) and the reaction is spontaneous. The more the negative value more will be its spontaneity.
2.Ans: B.-No, because the surrounding must have experienced an entropy increase that is numerically greater than the entropy decrease experienced by the system.
Let us consider a hot cup of tea with saucer in it to stop evaporating. By definition, as a system gets colder, entropy will decrease as it has lost heat. Now, as the tea cold the room gets warmer and increases its entropy. As we divide the small temperature, the entropy gain from the tea is greater than the entropy lost by the tea.
C-Ans: B-From the water to the ice, as heat is present in terms of energy which flows from hotter body to colder body.
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