(a) The correct statements about a compressed liquid are:
a. Lower pressures (P u, at a given P or T)
d. Higher specific enthalpies (h>h, at a given P or T)
e. Variation of properties with pressure is very mild.
f. Variation of properties with temperature is very mild.
A compressed liquid is a state of matter where the substance is in the liquid phase but at a pressure higher than its saturation pressure. In this state, the liquid is not boiling or evaporating, but it is compressed due to the high pressure. The statements (a), (d), (e), and (f) are all correct about compressed liquids.
(b) The exact state of a substance can be specified using different combinations of properties. The correct combination is:
c. Pressure and specific enthalpy (P and h)
By knowing the pressure and specific enthalpy, we can determine the exact state of the substance. Specific enthalpy is a measure of the energy content per unit mass of the substance. It combines the effects of pressure, temperature, and other properties. Therefore, by knowing the pressure and specific enthalpy, we can uniquely identify the state of the substance.
(c) To determine the specific volume of a two-phase liquid-vapor mixture, we can use the formula:
Specific volume = Total volume / Total mass
In this case, the total volume is given as 0.3 m³ and the total mass is the sum of the masses of saturated liquid and vapor, which are 2.8 kg and 3.2 kg, respectively. Plugging these values into the formula, we get:
Specific volume = 0.3 m³ / (2.8 kg + 3.2 kg)
Calculating this, we find that the specific volume of the mixture is approximately 0.05 m³/kg.
So, the correct answer is:
c. 0.05 m³/kg