A 15.0-L scuba diving tank contains a helium-oxygen (heliox) mixture made up of 23.0 g of He and 4.14 g of O2 at 298 K. Calculate the mole fraction of each component in the mixture.

Respuesta :

Answer: The mole fraction of Helium is 0.978 and that of oxygen gas is 0.022

Explanation:

To calculate the number of moles, we use the equation:

[tex]\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}[/tex]      .....(1)

  • For helium:

Given mass of helium = 23 g

Molar mass of helium = 4 g/mol

Putting values in equation 1, we get:

[tex]\text{Moles of helium}=\frac{23g}{4g/mol}=5.75mol[/tex]

  • For oxygen gas:

Given mass of oxygen gas = 4.14 g

Molar mass of oxygen gas = 32 g/mol

Putting values in equation 1, we get:

[tex]\text{Moles of oxygen gas}=\frac{4.14g}{32g/mol}=0.129mol[/tex]

Mole fraction of a substance is given by:

[tex]\chi_A=\frac{n_A}{n_A+n_B}[/tex]

  • For helium:

Moles of helium = 5.75 moles

Total moles = [5.75 + 0.129] = 5.879 moles

Putting values in above equation, we get:

[tex]\chi_{(He)}=\frac{5.75}{5.879}=0.978[/tex]

  • For oxygen gas:

Moles of oxygen gas = 0.129 moles

Total moles = [5.75 + 0.129] = 5.879 moles

Putting values in above equation, we get:

[tex]\chi_{(O_2)}=\frac{0.129}{5.879}=0.022[/tex]

Hence, the mole fraction of Helium is 0.978 and that of oxygen gas is 0.022

Considering the definition of mole fraction and molar mass, the mole fraction of He and O₂ in the mixture is 0.978 and 0.022 respectively.

The mole fraction is a dimensionless quantity that expresses the ratio of the number of moles of a component to the number of moles of all the components present.

The mole fraction of a gas in a gas mixture is given by:

[tex]x_{A} =\frac{n_{A} }{n_{T} }[/tex]

This fraction will always be less than 1.

On the other side, the molar mass is the amount of mass that a substance contains in one mole. This is:

[tex]molar mass=\frac{mass}{number of moles}[/tex]

Then, the number of moles can be calculated as:

[tex]number of moles=\frac{mass}{molar mass}[/tex]

In this case, you know:

  • Mass of helium = 23 g
  • Molar mass of helium = 4 g/mol
  • Mass of oxygen gas = 4.14 g
  • Molar mass of oxygen gas = 32 g/mol

So, the number of moles of each gas can be calculated as:

  1. Helium: [tex]number of moles of helium=\frac{23 g}{4 \frac{g}{mole} }= 5.75 moles[/tex]
  2. Oxygen: [tex]number of moles of oxygen=\frac{4.14 g}{32 \frac{g}{mole} }= 0.129 moles[/tex]

Being the total moles of moles 5.879 moles (5.75 moles of helium + 0.129 moles of oxygen), the mole fraction of each gas can be calculated as:

  • [tex]x_{He} =\frac{n_{He} }{n_{T} }=\frac{5.75 moles}{5.879 moles} =[/tex] 0.978
  • [tex]x_{O_{2} } =\frac{n_{O_{2} } }{n_{T} }=\frac{0.129 moles}{5.879 moles} =[/tex] 0.022

Finally, the mole fraction of He and O₂ in the mixture is 0.978 and 0.022 respectively.

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