Answer for PART A and PART B
Entropy and the Second Law of Thermodynamics
According to the second law of thermodynamics, all reactionsproceed spontaneously in the direction that increases totalentropy. The total entropy is defined as
%u0394Stotal=%u0394Ssystem+%u0394Ssurroundings
The direction of a spontaneous change is always determined bythe sign of the total entropy change:
-The reaction is spontaneous if %u0394Stotal>0.
-The reaction is nonspontaneous if %u0394Stotal<0.
-The reaction is at equilibrium if %u0394Stotal=0.
The value of %u0394Stotal depends on %u0394Ssystem and%u0394Ssurroundings, which are defined by%u0394Ssystem=S(products)%u2212S(reactants) and%u0394Ssurroundings= %u2212%u0394Hsystem/T
Spontaneity is therefore affected by the enthalpy of the systemand the Kelvin temperature.
********PartA
CaO can be used as a drying agent. One suchapplication occurs when water is added to dry concrete or cement.The reaction that occurs is
CaO(s)+H2O(l)%u21CCCa(OH)2(s)
The product is commonly called slaked lime.
Assuming the commonly used standard-state temperature of25%u2218C,calculate %u0394Stotal for this reaction using tablefrom the table below.
| Substance | S%u2218
[J/(K%u22C5mol)] | %u0394H%u2218f
(kJ/mol) |
| CaO(s) | 39.9 | %u2212635.1 |
| H2O(l) | 69.9 | %u2212285.8 |
| Ca(OH)2(s) | 83.4 | %u2212986.1 |
Express your answer to threesignificant figures and include the appropriate units.
*********PartB
A particular solvent with %u0394S%u2218vap=112.9J/(K%u22C5mol) and %u0394H%u2218vap=38.0kJ/mol is being consideredfor an experiment. In the experiment, which is to be run at 75%u2218C, the solvent must not boil. Basedon the total entropy change associated with the vaporizationreaction, would this solvent be suitable and why or why not?
The solvent would
A particular solvent with and is being considered for anexperiment. In the experiment, which is to be run at 75 , thesolvent must not boil. Based on the total entropy change associatedwith the vaporization reaction, would this solvent be suitable andwhy or why not?
| be suitable because %u0394Stotal>0. |
| not be suitable because %u0394Stotal>0. |
| be suitable because %u0394Stotal<0. |
| not be suitable because %u0394Stotal<0. |
