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A mixture of methane gas, CH4(g) , and pentane gas, C5H12(g) , has a pressure of 0.5239 atm when placed in a sealed container. The complete combustion of the mixture to carbon dioxide gas, CO2(g) , and water vapor, H2O(g) , was achieved by adding exactly enough oxygen gas, O2(g) , to the container. The pressure of the product mixture in the sealed container is 2.429 atm . Calculate the mole fraction of methane in the initial mixture, assuming the temperature and volume remain constant.

Answer :

Answer:0.86

Explanation:

A mixture of methane gas, CH4(g), and pentane gas, C5H12(g), has a pressure of 0.5922 atm when placed in a sealed container.Lets suppose initially partial pressure of CH4 is x and C5H12 is y

x+y=0.5922-----i

1.CH4[g] + 2O2[g] -> CO2[g] + 2 H2O[g]

2.C5H12 + 8O2 → 5CO2 + 6H2O

partial pressure of CH4 is x produce xatm of CO2 and 2xatm of H2O

x + 2x = 3 atm

partial pressure of C5H12 is y produce 5yatm of CO2 and 6yatm of H2O

5y+6y=11y

so the final partial pressure of product mixture will be

3x + 11y = 2.429atm ------ii

solve eq i for x and put in ii

x=0.5922-y -----iii

3(0.5922-y)+ 11y = 2.429atm

y= 0.8155atm

put in iii

x=0.5922-0.8155

x= 0.51atm (Partial pressure of CH4)

mol fraction of CH4=Partial pressure/

Total pressure

=0.51/0.5922

=0.86.

Eduard22sly

The mole fraction of methane, CH₄ in the initial mixture is 0.795

Let the partial pressure of methane, CH₄ be u

Let the partial pressure of pentane, C₅H₁₂ be v

The total pressure of the mixture is 0.5239 atm i.e

Partial pressure of methane + partial pressure of pentane = 0.5239 atm

u + v = 0.5239..... (1)

Combustion reaction of the mixture.

For methane CH₄:

CH₄ + 2O₂ —> CO₂ + 2H₂O

From the balanced equation above,

u atm of CH₄ produced u atm of CO₂ and 2u atm of H₂O.

Thus, the partial pressure of CH₄ produces = u + 2u = 3u atm of the products.

For pentane C₅H₁₂:

C₅H₁₂ + 8O₂ —> 5CO₂ + 6H₂O

From the balanced equation above,

v atm of C₅H₁₂ produced v atm of CO₂ and 6v atm of H₂O.

Thus, the partial pressure of C₅H₁₂ produces = 5v + 6v = 11v atm of the products.

Summary:

CH₄ produced 3u atm

C₅H₁₂ produced 11v atm

But the total pressure of the products is 2.429 atm.

Thus,

3u + 11v = 2.429......... (2)

Next, we shall determine the partial pressure of methane, CH₄ i.e u.

u + v = 0.5239 ......... 1

3u + 11v = 2.429 ........2

From equation 1,

v = 0.5239 – u

Substitute v into equation 2

3u + 11v = 2.429

3u + 11(0.5239 – u) = 2.429

3u + 5.7629 – 11u = 2.429

Collect like terms

3u – 11u = 2.429 – 5.7629

–8u = –3.3339

Divide both side by –8

u = –3.3339 / –8

u = 0.4167 atm

Therefore, the partial pressure of methane, CH₄ in the initial mixture is 0.4167 atm.

Finally, we shall determine the mole fraction of methane CH₄ in the initial mixture.

Partial pressure of methane, CH₄ = 0.4167 atm.

Total pressure = 0.5239 atm

Mole fraction of methane CH₄ =?

Mole fraction = partial pressure / Total pressure

Mole fraction of methane CH₄ = 0.4167 / 0.5239

Mole fraction of methane CH₄ = 0.795

Therefore, the mole fraction of methane CH₄ in the initial mixture is 0.795

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