Answer:
a. ΔU = 42.2 KJ
b. ΔU = 34689.75 J = 34.7 KJ
Explanation:
a.
For a constant volume process:
ΔQ = ΔU
where,
ΔQ = Heat Supplied to the system
ΔU = Change in internal energy
but.
ΔQ = (Heat Transfer Rate)(Time Duration)
ΔQ = (10 Btu/min)(4 min)
ΔQ = (40 Btu)(1.055 KJ/1 Btu)
ΔQ = 42.2 KJ
Therefore, the equation becomes:
ΔU = 42.2 KJ
b.
For a constant pressure process:
ΔQ = ΔU + PΔV
ΔU = ΔQ - PΔV
where,
ΔV = Change in volume = (Surface Area)(Displacement) = (100 cm²)(15 cm)
ΔV = (1500 cm³)(10⁻⁶ m³/1 cm³) = 1.5 x 10⁻³ m³
P = Pressure = (20 atm)(101325 Pa/1 atm) = 2.0265 x 10⁶ Pa
ΔQ = Heat transferred to Gas = (30 Btu)(1055 J/1 Btu) = 31650 J
ΔU = Change in Internal Energy = ?
Therefore,
ΔU = 31650 J + (2.0265 x 10⁶ Pa)(1.5 x 10⁻³ m³)
ΔU = 31650 J + 3039.75 J
ΔU = 34689.75 J = 3.47 KJ
