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  • Help me understand! For which of the following processes, ΔS is negative ?

For which of the following processes, ΔS  is negative ?

  • Option 1)

    H_{2}(g)\rightarrow 2H(g)

  • Option 2)

    N_{2}(g,1 atm)\rightarrow N_{2}(g,5atm)

  • Option 3)

    C(diamond)\rightarrow C(graphite)

  • Option 4)

    N_{2}(g,273 K)\rightarrow N_{2}(g, 300K)

 

Answers (1)

best_answer

As we have learned

Change in entropy for ideal gas in terms of C(p) -

\Delta S_{system}= nC_{P}\ln \frac{T_{f}}{T_{i}}+nR\ln \frac{P_{i}}{P_{f}}

- wherein

C_{p}= Molar heat capacity at constant pressure

 

 

 

N_{2}(g)(1 Atm)\rightarrow N_{2}(g)(5atm)

\Delta s = (nC_{p} ln\frac{T_{2}}{T_{1}})+nRln\frac{V_{2}}{V_{1}}

for isothermal process T_{1}=T_{2}

V_{2}/V_{1}= P^{1}/P^{2}

\Delta s = 0+ nR ln \frac{P_{1}}{P_{2}}

\Delta s = 0+ nR ln \frac{1}{5}

\Delta s < 0

 

 

 

 

 


Option 1)

H_{2}(g)\rightarrow 2H(g)

This is incorrect

Option 2)

N_{2}(g,1 atm)\rightarrow N_{2}(g,5atm)

This is correct

Option 3)

C(diamond)\rightarrow C(graphite)

This is incorrect

Option 4)

N_{2}(g,273 K)\rightarrow N_{2}(g, 300K)

This is incorrect

Posted by

divya.saini

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