1) The condition for a reaction to proceed spontaneously at constant pressure an
ID: 700609 • Letter: 1
Question
1) The condition for a reaction to proceed spontaneously at constant pressure and temperature is that the change in Gibbs free energy (delta-G) for the reaction is less than zero.
The Gibbs free energy change is given by:
delta-G = delta-H - T*delta-S
where T is the absolute temperature (i.e., in kelvins).
We are given delta-H and delta-S for this reaction (the units should probably be in kJ/mole and J/(mol*K) respectively, not J and J/K), and need to find the temperature range (if it exists) for which delta-G is negative. That is,
0 > delta-G = -5500 J/mol - (-25 J/(mol*K)) * T
5500 K > 25 *T
220 K > T
Answer (b) is the correct one.
2) the answer is D) because it's the only solution in the list that doesn't contain any of the ions Ag or CrO that can disrupt the solubility of Ag2CrO4 (Silver Chromate). The rest of the solutions have either Ag or CrO in them that may decrease the molar solubility of Ag2CrO4.
In addition, according to Le Chatelier's Law concerning equilibrium, any stress put on a system at equilibrium will cause the system to shift to counteract that change. So when Ag2CrO4 is added to a solution and dissociates, the free Ag or CrO4 ions in the other solutions added to the product side will cause the system to shift to the left, using up the ions in the process and producing more of the reactant Ag2CrO4 which is why free ions can disturb the molar solubility of a substance.
Ag2CrO4 <~~> 2Ag(+) + CrO4(2-)
ANSWER (D)
Explanation / Answer
CHEM 2102 Final Exam Fall 2015 Time allowed: 3 hr 28) For a particular chemical reaction AH-55 ki and AS "-25 J/K. under what temperature condition is the reaction spontaneous? a) only when T
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