Final answer:
The missing unit for temperature when an ideal gas is heated in a steady-flow heat exchanger is Kelvins (K), which is the unit used for thermodynamic temperature in equations involving ideal gas properties.
Step-by-step explanation:
An ideal gas, cp = (7/2)r, is heated in a steady-flow heat exchanger from 70. The missing unit for temperature is Kelvins (K).
When dealing with ideal gases and their properties, the unit used for temperature is always Kelvins. This is important because the ideal gas law, thermodynamic equations, and specific heat calculations rely on an absolute temperature scale. As such, the specific heat at constant pressure (Cp) and other gas properties are typically given in terms of an absolute scale where 0 K (Kelvin) represents absolute zero.