What is the change in entropy when 0.7 m3 of CO2 and 0.3 m3 of N2, each at 1 bar and 25°C, blend to form a gas mixture at the same conditions? Assume ideal gases

Respuesta :

Explanation:

The given data is as follows.

        P = 1 bar,     T = 298 K

For [tex]CO_{2}[/tex];  [tex]V_{1C} = 0.7 m^{3}[/tex]

For [tex]N_{2}[/tex];    [tex]V_{1N} = 0.3 m^{3}[/tex]

Therefore, final volume will be as follows.

           [tex]V_{1C} + V_{1N} = 1 m^{3} = V_{2}[/tex]

Hence,            [tex]V_{2} = 1 m^{3}[/tex]

Formula for change in entropy is as follows.

          dS = [tex]nR ln (\frac{V_{2}}{V_{1}})[/tex]

For [tex]CO_{2}[/tex],  [tex]PV_{1C} = nRT[/tex]

or,         [tex]nR = \frac{PV_{1C}}{T}[/tex]            

                       = [tex]\frac{10^{5} \times 0.7}{298}[/tex]        

                       = 234.89

      [tex]dS_{CO_{2}} = 234.89 \times \frac{1}{0.7}[/tex]  

                       = 83.77 J/K

For [tex]N_{2}[/tex],       nR = [tex]\frac{P_{1}V_{1}N}{T}[/tex]

                  = [tex]\frac{10^{5} \times 0.3}{298}[/tex]

                  = 100.67

       [tex]dS_{N_{2}} = 100.67 ln (\frac{1}{0.3})[/tex]

                   = 121.20 J/K

Now, total change in the entropy is calculated as follows.

               dS = [tex]dS_{CO_{2}} + dS_{N_{2}}[/tex]

                    = (83.77 + 121.20) J/K

                    = 204.97 J/K

Thus, we can conclude that the change in entropy is 204.97 J/K.

Entropy change will be 204.97 J/K.

Firstly, let's write the given values:

Since, it's an ideal gas therefore;

  • P=1 bar
  • T=298 K
  • For CO₂= [tex]V_{CO_2} = 0.7m^3[/tex]
  • For N₂= [tex]V_{N_2}=0.3 m^3[/tex]

Thus, the final volume will be V₂= [tex]0.7+0.3=1m^3[/tex]

What does change in entropy mean?

Entropy change can be defined as the change in the state of disorder of a thermodynamic system that is associated with the conversion of heat or enthalpy into work.

Entropy change can be calculated by using the given formula:

[tex]\text{dS}=n R ln \frac{V_2}{V_1}[/tex]

⇒For CO₂,

From ideal gas equation it is known that: pV=nRT

∴ nR=pV/T

[tex]nR=\frac{10^5 *0.7}{298} =234.89[/tex]

So, entropy change for CO₂ will be:

[tex]dS_{CO_2}=234.89ln (\frac{1}{0.7} )=83.77J/K[/tex]

⇒For N₂,

[tex]nR=\frac{10^5*0.3}{298} =100.67[/tex]

So, entropy change for N₂ will be:

[tex]dS_{N_2}=100.67 ln(\frac{1}{0.3}) =121.20 J/K[/tex]

Now, total entropy change can be calculated as:

[tex]dS_{Total}=dS_{CO_2}+dS_{N_2}\\\\=83.77+121.20\\\\=204.97 J/K[/tex]

Thus, entropy change will be 204.97 J/K.

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