CHMA11H3 Lecture Notes - Lecture 23: Standard Molar Entropy, Zero Point Railway Station, Thermodynamics

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erinsea-lion742

28 Feb 2019

School

UTSC

Department

Chemistry

Course

CHMA11H3

Professor

Nirusha Thavarajah, Scott M. Ballantyne, Ruby May Sullan

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CHMA11H3 Lecture Notes - Lecture 22: Spontaneous Process, Enthalpy, Thermodynamics

CHMA11H3 Lecture Notes - Lecture 23: Standard Molar Entropy, Zero Point Railway Station, Thermodynamics

CHMA11H3 Lecture Notes - Lecture 24: Stepwise Reaction, Chemical Equation

Document Summary

Ssurroundings: remember the 2nd law of thermodynamics, all spontaneous processes will produce increases in the entropy of the universe, therefore. Suniverse will always be greater than 0: quantifying the entropy of systems, the absolute entropy of a substance can be measured. 0: standard molar entropy: the absolute entropy of 1 mole of a pure substance in its standard state at 25 degrees celsius and 1 atm, represented by so. In these cases the entropy of the surroundings will increase: endothermic processes: heat is absorbed from the surroundings. In these cases, the entropy of the surroundings will decrease: the magnitude of the change in the entropy of the surroundings ins inversely proportional to temperature, can be expressed in the following equation. Ssurrounding = - hsystem / t: we assume temperature and pressure are both constant, therefore we can study the temperature dependence of entropy, example: looking at water going from liquid to solid form.

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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.

rosefrog182

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

The solvent would

	be suitable because %u0394Stotal>0.
	not be suitable because %u0394Stotal>0.
	be suitable because %u0394Stotal<0.
	not be suitable because %u0394Stotal<0.

blackgoat894

CHMA11H3 Lecture Notes - Lecture 23: Standard Molar Entropy, Zero Point Railway Station, Thermodynamics

CHMA11H3 Lecture Notes - Lecture 22: Spontaneous Process, Enthalpy, Thermodynamics

CHMA11H3 Lecture Notes - Lecture 23: Standard Molar Entropy, Zero Point Railway Station, Thermodynamics

CHMA11H3 Lecture Notes - Lecture 24: Stepwise Reaction, Chemical Equation

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