Question

An expansion process on a diatomic ideal gas (C_v = 5/2 R), has a linear path between the initial and final coordinates on a pV diagram. The coordinates of the initial state are: the pressure is 300 kPa, the volume is 0.08 m³ and the temperature is 390 K. The final pressure is 90 kPa and the final temperature s 320 K. The change in the internal energy of the gas, in SI units, is closest to:

पर्याय

• -11,000

• -6500

• 11,000

• zero

Answer 1

-11,000

Explanation:

ΔU = nC_v ΔT

= n `5/2`R (T_f - T_i)

n = `("P"_1"V"_1)/("RT"_1)`

ΔU = `("P"_1"V"_1)/("RT"_1)xx5/2` R (T₂ - T₁)

= `(300xx10^3xx0.08)/390xx5/2(320-390)`

= `(15xx10^3xx0.08xx5)/39xx(-70)`

= `-0.40/39xx15xx10^3xx70`

= `-40/39xx150xx70`

= `-40/39xx10500`

ΔU = -11000 Joule