3. Explain why, for a gas, the specific heat at constant volume has a different value 
from the specific heat at constant pressure.
An ideal gas is contained in a cylinder fitted with a piston. Initially the temperature of the 
gas is 15℃. If the mass of the gas is 0.035 kg, calculate the quantity of heat energy 
required to raise the temperature of the gas to 150 ℃ when:
(a) The piston is fixed;
(b) The piston moves and the pressure is constant.
For the gas, 𝑐𝑣 = 676 J/kg-K and 𝑐𝑝 = 925 J/kg-K.

A piston–cylinder assembly contains air modeled
as an ideal gas with a constant specific heat ratio, k =
1.4. The air undergoes a power cycle consisting of
four processes in series: Process 1–2: Constanttemperature expansion at 600 K from p1 = 0.5 MPa to
p2 = 0.4 MPa. Process 2–3: Polytropic expansion with
n = 1.35 to p3 = 0.3 MPa. Process 3–4: Constantpressure compression to V4 = V1. Process 4–1:
Constant-volume heating. Determine (a) the work and
heat transfer for each process, in kJ/kg, and (b) the
thermal efficiency. 

An ideal Otto cycle has a compression ratio of 10.5, takes in air at 90 kPa and , and is repeated 2500 times per minute. Using constant specific heats at room temperature, determine the thermal efficiency of this cycle and the rate of heat input if the cycle is to produce 90 kW of power.

An ideal Otto cycle with Argon as the working fluid has a compression ratio of 6.8. The minimum and maximum temperatures in the cycle are 450 R and 2,260 R. Assuming constant specific heats, determine

(a) the amount of heat transferred to the argon during the heat-addition process

(b) the thermal efficiency

(c) the thermal efficiency of a Carnot cycle operating between the same temperature limits