Answer the following questions based on the P-T phase diagram of carbon dioxide:
(a) At what temperature and pressure can the solid, liquid and vapour phases of \( CO_2\) co-exist in equilibrium?
(b) What is the effect of the decrease of pressure on the fusion and boiling point of \( CO_2\)?
(c) What are the critical temperature and pressure for \( CO_2\)? What is its significance?
(d) Is \( CO_2\) solid, liquid or gas at
(a) –70°C under 1 atm,
(b) –60°C under 10 atm,
(c) 15°C under 56 atm?
(a) Liquid and vapour phases of CO2 co-exist at the triple point temperature
= – 56.6°C and pressure = 5.11 atm.
(b) Both the boiling point and freezing point of CO2 decrease if pressure decreases.
(c) The critical temperature and pressure of CO2 are 31.1°C and 73.0 atm, respectively.
Above this temperature, CO2 will not liquefy even if compressed to high pressures.
(d) (a) vapour (b) solid (c) liquidAnswered by Pragya Singh | 1 year ago
Explain why :
(a) a body with large reflectivity is a poor emitter
(b) a brass tumbler feels much colder than a wooden tray on a chilly day
(c) an optical pyrometer (for measuring high temperatures) calibrated for an ideal black body radiation gives too low a value for the temperature of a red hot iron piece in the open, but gives a correct value for the temperature when the same piece is in the furnace
(d) the earth without its atmosphere would be inhospitably cold
(e) heating systems based on the circulation of steam are more efficient in warming a building than those based on the circulation of hot water
A brass boiler has a base area of 0.15 m2 and thickness 1.0 cm. It boils water at the rate of 6.0 kg/min when placed on a gas stove. Estimate the temperature of the part of the flame in contact with the boiler. Thermal conductivity of brass = 109 J s–1 m–1 K–1; Heat of vaporisation of water = 2256 × 103 J kg–1.
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 the co-efficient of thermal conductivity of thermacole is 0.01 J s–1 m–1 K–1. [Heat of fusion of water = 335 × 103 J kg–1]