The average degree of freedom per molecule for a gas is 6. The gas performs 25 J of work when it expands at constant pressure. The heat absorbed by the gas is:
Correct answer: B. 100 J
- A. 75 J
- B. 100 J
- C. 150 J
- D. 125 J
Explanation
According to the first law of thermodynamics, the change in internal energy (ΔU) is equal to the heat absorbed (Q) minus the work done (W), i.e., ΔU = Q - W. For a gas with an average degree of freedom per molecule, the relation for the specific heat capacity at constant pressure (Cp) can be derived considering the degrees of freedom. With 6 degrees of freedom, Cp = (7/2)R per mole. The work done by the gas at constant pressure is given as 25 J. By applying the first law and considering the relationship between Cp, Q, and W, the heat absorbed by the gas is calculated to be 100 J. Options A, C, and D do not align with this derivation, leading to incorrect conclusions about the heat absorbed.
Report an error
The more specific you are, the faster it gets fixed. A source beats an opinion.
Prefer email? [email protected]
About Molar Specific Heat of a Gas
Molar specific heat is the heat required to raise the temperature of one mole of a gas by one kelvin, expressed through Q = nCΔT. Questions compare the constant volume value Cv with the constant pressure value Cp, apply the ideal gas relation Cp − Cv = R, and identify how the thermodynamic process affects heat capacity.
Practise Thermodynamics
714 free Thermodynamics MCQs from Physics, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Discussion
Stuck on an option, or know a faster way to get there? Ask or explain it here.
No comments yet. Be the first to explain this one.
Exams that ask Physics questions like this
Physics is on 16 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.
More Molar Specific Heat of a Gas questions
A mixture of ideal gases N2 and He are taken in the mass ratio of 14 : 1 respectively. Molar heat capacity of the mixture at constant pressure is:
Molecule of a gas can be modelled as three sphere connected through three rigid rods as to make triangle like structure. A gas containing such molecules performs 25 J of work when it expands at constant pressure. Heat given to gas is:
2 mole of an ideal monoatomic gas mix with 1 mole of a ideal diatomic gas. The Cp/Cv for the mixture is:
One mole of an ideal monoatomic gas is mixed with one mole of an ideal diatomic gas. The molar specific heat of this mixture at constant volume is:
The specific heat of Ar at constant volume is 0.075 kcal kg-1 K-1. Calculate the atomic weight (R = 2 cal mol-1 K-1)
Two cylinders of equal size are filled with equal amount of ideal diatomic gas at room temperature. Both the cylinders are fitted with pistons. In cylinder A the piston is free to move, while in cylinder B the piston is fixed. When the same amount of heat is added to cylinder A, it raises by 20 K. What will be the rise temperature of gas in cylinder B?