A gas expands and does PV work on its surroundings equal to 344 J. At the same time, it absorbs 139 J of heat from the surroundings. Calculate the change in energy of the gas. Note: PV work means work done by a changing volume against constant pressure. Enter your answer in scientific notation.

Respuesta :

Explanation:

According to first law of thermodynamics, total energy of a system and its surroundings remain constant.

Equation for first law of thermodynamics is as follows.

             [tex]\Delta U = q + w[/tex]

where,       [tex]\Delta U[/tex] = change in energy

                                q = heat released or absorbed

                                 w = work done

As it is given that heat absorbed is 139 J (as heat is absorbed so it will be positive) and work done is -344 J (as work is done on the system).

Hence, we will calculate the energy change as follows.

                    [tex]\Delta U = q + w[/tex]

                                 = 139 J + (-344 J)

                                 = 205 J

Thus, we can conclude that change in energy of the gas is 205 J.                

The change in energy of the gas is -2.05 × 10^-2 J.

According to the first law of thermodynamics, energy is neither created nor destroyed. From this law, the total energy of the system is given by;

ΔU = Q + W

Where;

ΔU = change in energy of the system

Q = heat absorbed or lost

W = work done

Recall that work done is negative when work is done on the surrounding and Q is negative when heat is lost to the surroundings.

Given that;

Q = 139 J

W = -344 J

ΔU = 139 J - 344 J

ΔU = -2.05 × 10^-2 J

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