A spherical balloon of volume 3.92 103 cm3 contains helium at a pressure of 1.25 105 Pa. How many moles of helium are in the balloon if the average kinetic energy of the helium atoms is 3.60 10^-22 J?

Respuesta :

Answer:

3.39

Explanation:

Given that

Volume, v = 3.92*10^3 cm³ we convert the volume from cm³ to m³ and we have 0.00392

Pressure, P = 1.25*10^5 Pa

Average Kinetic Energy, K.E = 3.6*10^-22 J

We use the gas law formula,

PV = nRT

Making n subject of the formula, we have

n = PV/RT

Solving for n, we have

n = (1.25*10^5 Pa * 0.00392 m³) / 8.314 * T

n = 4.9*10^8 / 8.314 * T

n = 490 / 8.314T

n = 58.94/T

Note that average kinetic energy is given as

K.E(avg) = 3/2K.T,

3/2 K.T = 3.6*10^-22 J

where K = 1.38*10^-23

T = (3.6*10^-22 J * 2) / (3 * 1.38*10^-23)

T = 17.39

Substitute for T, we have

n = 58.94 / 17.39

n = 3.39

Lanuel

The number of moles of helium that are in the spherical balloon is equal to 3.39 moles.  

Given the following data:

  • Volume = [tex]3.92 \times 10^3\;cm^3[/tex] to [tex]m^3 = 3.92 \times 10^{-3}\;m^3[/tex]
  • Pressure = [tex]1.25 \times 10^5\;pa[/tex]
  • Average kinetic energy = [tex]3.60 \times 10^{22}\;J[/tex]

Scientific data:

  • Boltzmann constant (k) = [tex]1.38 \times 10^{-23}\;J/K[/tex]
  • Ideal gas constant, R = 8.314 J/molK

To determine the number of moles of helium that are in the balloon, we we would use the ideal gas law equation;

[tex]n=\frac{PV}{RT}[/tex]   ...equation 1.

Where;

  • P is the pressure.
  • V is the volume.
  • n is the number of moles of substance.
  • R is the ideal gas constant.
  • T is the temperature.

First of all, we would determine the temperature of the spherical balloon by using this formula:

[tex]T=\frac{2}{3} \frac{K_E}{k} \\\\T = \frac{2}{3}\times \frac{3.60 \times 10^{-22}}{1.38 \times 10^{-23}} \\\\T = \frac{2}{3}\times 26.09\\\\T=17.39\;K[/tex]

Temperature, T = 17.39 K

Substituting the parameters into eqn. 1, we have;

[tex]n=\frac{1.25 \times 10^5\times 3.92 \times 10^{-3}}{8.314 \times 17.39}\\\\n=\frac{490}{144.58}[/tex]

n = 3.39 moles.

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