A ‘thermacole’ icebox is a cheap and an efficient method for storing small quantities of cooked food in summer in particular. A cubical icebox of side 30 cm has a thickness of 5.0 cm. If 4.0 kg of ice is put in the box, estimate the amount of ice remaining after 6 h. The outside temperature is 45 °C, and co-efficient of thermal conductivity of thermacole is 0.0 s¯¹m–1 K¯¹. [Heat of fusion of water = 335 × 103 J kg¯¹]
The P − T phase diagram of CO 2 is given below.
a)
At 1 atm pressure and temperature of − 60 ° C , CO 2 lies to the left of triple point C which is the region of vaporous and solid phases. Thus, it cannot go through a liquid phase.
b)
When CO 2 at 4 atm pressure is cooled from room temperature at constant pressure it condenses to solid directly. This happens because at 4 atm pressure, CO 2 is below its triple point and in this region it exists in vaporous and solid phases.
c)
When a solid mass of CO 2 at 10 atm pressure and − 65 ° C temperature is heated up to a room temperature at constant pressure, it can be observed in the P − T phase diagram that it will form a line parallel to the T axis. So, CO 2 changes from solid phase to liquid phase and then to vaporous phase.
d)
If CO 2 is heated to 70 ° C and then compressed isothermally, then it will not exhibit any transition to the liquid phase. This is because, 70 ° C is higher than the critical temperature of CO 2 . Even though it remains in the vapour state, its behavior will depart from its ideal behavior as the pressure increases.
The
a)
At
b)
When
c)
When a solid mass of
d)
If
