Which of the following statements regarding spontaneous processes are true? a. S

Question

Which of the following statements regarding spontaneous processes are true? a. Spontaneous processes are exothermic. b. Spontaneous processes proceed without outside intervention once initiated. c. Spontaneous reactions are not always rapid. d. The motional freedom of particles tends to increase during spontaneous change. e. Particles tend to become more spread out during spontaneous change. According to the second law of thermodynamics, the entropy change in an isolated system (Delta S_sys) during a spontaneous process must be ___ Given one mole of each of the following, which of the following has the highest number of accessible microstates? a. Ice, H_2O(s), at 273 K b. Liquid water, H_2O(l), at 373 K c. Steam, H_2O(g), at 373 K d. Propane, CH_3CH_2CH_3(g), at 373 K e. Butane, CH_3CH_2CH_2CH_3(g), at 373 K The enthalpy of vaporization of water at 100.0 degree C is 40.68 kJ/mol. What is the entropy change in the universe when one mole of water vapor condenses at 100.0 degree C in a large room maintained at a temperature of 25.00 degree C?

Explanation / Answer

a)false :

spontaneous process may or may not be exothermic it only depends on gibbs free energy of the system if it is negative then the process is spontaneous
b)true
c)true :

rusting of iron happens very slow rate but is a spontaneous process as once started it dosen't need any assitance for rusting to occur
or

C(s,diamond)C(s,graphite) in years

d)false:
for a spontaneous process total entropy of universe must increase for spontaneous process but the entropy of system may or may not increase for example in adsorption translational motion of gas is reduced to zero
Suniverse=Ssystem+Ssurroundings > 0

e)false :
adsorption is a spontaneous process but here degree of freedom reduces for adsorbent
but overall degree of freedom of system + surrounding is greater than zero

2)
positive

in isolated system there is no interaction from the surroundings and for a spontaneous process

system + surrounding is greater than zero

here surrounding entropy change is zero so system entropy change must be greater than zero
3) d
butane should have maximum accessible microstates as it has more degree of motion viz. translational,rotaional,rolling motion etc. as well as it is in gaseous state

4)here Ts = 100 + 273 = 373 K for steam condensation
         and for room temperature Tr = 25 + 273 = 298 K

here heat change is same 40.68 kJ/mol = 40680 J/mol

entropy = heat(q)/temperature(T)

system = (-40680 J/mol)/373 K = -109.06 J/mol.K heat is negative as it is absorbed
surroundings = (40680 J/mol)/298 K =136.51 J/mol.K

total entropy = system + surroundings = 27.45 J/mol.K

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