Use the data from this table of thermodynamic properties to calculate the values of δs°rxn for each of the following reactions at 25 °c.
a) 4nh3(g) + 7o2(g) > 4no2(g) + 6h2o(g) delta s rxn =?
b) 2h2o2(l) --> 2h2o(l) +o2 (g) delta s rxn =?

A) ΔSºrxn = - 112.5 J/molK

B) ΔSºrxn =- 120.48 J/molK

Explanation:

For an general equation aA + bB → cC + dD

ΔSºrxn = cSºC + dSºD -  aSºA - bSºB

Using a table of thermodynamic properties in J/molK like Petrucci 8th Ed

A) ΔSºrxn = (4*240,1) + (6*188,8) - (4*192,5)- (7*205,1)= - 112.5 J/molK

B) ΔSºrxn= (2*69,91) + (1*205,1) - (2*232,7)= -120.48 J/molK

Be careful with the states of matter

A. ∆S ° (reaction) = -113 J / mol K

B. ∆S ° (reaction) = 125.8 J / mol K

Entropy (with the symbol S) in thermodynamics indicated the degree of system disorder

Entropy like other thermodynamic terms can only be calculated from the initial and final changes

Entropy will also change in the process of changing energy forms

The value of ΔS ° can be calculated from standard entropy data

From the CRC Handbook of Chemistry and Physics data table, 84th Edition (2004) we can find out the Standard thermodynamic Quantities for Chemical Substances at 25 ° C for entropy: (sources can be obtained from other data)

NH₃ (g) = 192.8 J / mol K

O₂ (g) = 205 J / mol K

H₂O (g) = 188.8 J / mol K

H₂O (l) = 70 J / mol K

NO₂ (g) = 240.1 J / mol K

H₂O₂ (l) = 109.6 J / mol K

∆S ° (reaction) = {4.S ° NO₂ (g) + 6.S ° H₂O (g)} - {4.S ° NH₃ (g) + 7.S ° O₂ (g)}  

∆S ° (reaction) = {4. 240.1 + 6,188.8} - {4. 192.8 + 7,205}  

∆S ° (reaction) = -113 J / mol K  

∆S ° (reaction) = {2.S ° H₂O (l) + 1.S ° O₂} - {2.S ° H₂O₂ (l)}  

∆S ° (reaction) = {2.70+ 1,205} - {2,109.6}  

∆S ° (reaction) = 125.8 J / mol K

Delta H solution  

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an exothermic reaction  

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as endothermic or exothermic  

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away from the curb

explanation:

the wheels would then hit the curb if it started to rolling, decreasing the chance of an accident.

it can be observed without changing the identity of the object.

it depends on what substance you're talking about as well as many other factors. in quantum mechanics, the observation of particles affects the observers ability to measure certain properties. for example: you can know the velocity of a particle, but you can't know it's position; or you can know it's position, but not it's velocity. it's like trying to find out where a grain of sand is by throwing other grains of sand at it. once you find out where it is, it's been moved. it's also like trying to find an answer to the question of whether or not a tree falling in a forest makes a sound if nobody is there to hear it. paradoxically, the only way to find out is to be there and hear it.