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Grade 11Thermal Physics

A 4.34-mol sample of an ideal diatomic gas experiences a temperature increase of 62.4 K under constant pressure conditions. (a) How much heat was added to the gas? (b) By how much did the internal energy of the gas increase? (c) By how much did the internal translational kinetic energy of the gas increase?

Profile image of Radhika Batra
11 Years agoGrade 11
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1 Answer

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ApprovedApproved Tutor Answer1 Year ago

To tackle your question about the ideal diatomic gas, we need to apply some fundamental principles of thermodynamics. Let's break it down step by step, addressing each part of your question clearly.

Calculating Heat Added to the Gas

For an ideal gas undergoing a temperature change at constant pressure, the heat added can be calculated using the formula:

Q = n * Cp * ΔT

Where:

  • Q = heat added (in joules)
  • n = number of moles of gas (4.34 mol)
  • Cp = molar heat capacity at constant pressure for a diatomic gas (approximately 29.1 J/(mol·K))
  • ΔT = change in temperature (62.4 K)

Plugging in the values:

Q = 4.34 mol * 29.1 J/(mol·K) * 62.4 K

Calculating this gives:

Q ≈ 4.34 * 29.1 * 62.4 ≈ 7983.7 J

Change in Internal Energy

The change in internal energy (ΔU) for an ideal gas can be calculated using the formula:

ΔU = n * Cv * ΔT

For a diatomic gas, the molar heat capacity at constant volume (Cv) is approximately 20.8 J/(mol·K). Now we can calculate the change in internal energy:

ΔU = 4.34 mol * 20.8 J/(mol·K) * 62.4 K

Calculating this gives:

ΔU ≈ 4.34 * 20.8 * 62.4 ≈ 5644.5 J

Increase in Internal Translational Kinetic Energy

The increase in internal translational kinetic energy is directly related to the change in internal energy for an ideal gas, as internal energy primarily consists of kinetic energy contributions. Therefore, for a diatomic gas, the increase in translational kinetic energy is equal to the increase in internal energy:

Increase in Translational Kinetic Energy = ΔU

Thus, the increase in internal translational kinetic energy is:

≈ 5644.5 J

Summary of Results

  • Heat added to the gas (Q): ≈ 7983.7 J
  • Increase in internal energy (ΔU): ≈ 5644.5 J
  • Increase in internal translational kinetic energy: ≈ 5644.5 J

This breakdown should give you a clear understanding of how to approach problems involving heat transfer and changes in internal energy for ideal gases. If you have any further questions or need clarification on any part, feel free to ask!