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प्रश्न
Answer the following questions based on the P–T phase diagram of CO2:
What happens when CO2 at 4 atm pressure is cooled from room temperature at constant pressure?
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उत्तर १
It condenses to solid directly.
Explanation:
At 4 atm pressure, CO2 lies below 5.11 atm (triple point C). Hence, it lies in the region of vaporous and solid phases. Thus, it condenses into the solid state directly, without passing through the liquid state.
उत्तर २
CO2 at 4.0 atm pressure and room temperature (say, 27 °C) is in vapour phase. This point (4.0 atm, 27°C) lies below the vaporation curve OC and to the right of the triple point O. Therefore, when CO2 is cooled at this point at constant pressure, the point moves perpendicular to the pressure-axis and enters the solid phase region. Hence, the CO2 vapour condenses directly to solid phase without going through the liquid phase.
संबंधित प्रश्न
A copper block of mass 2.5 kg is heated in a furnace to a temperature of 500 °C and then placed on a large ice block. What is the maximum amount of ice that can melt? (Specific heat of copper = 0.39 J g–1 K–1; heat of fusion of water = 335 J g–1).
Answer the following questions based on the P–T phase diagram of CO2:
CO2 at 1 atm pressure and temperature – 60 °C is compressed isothermally. Does it go through a liquid phase?
Answer the following questions based on the P–T phase diagram of CO2:
Describe qualitatively the changes in a given mass of solid CO2 at 10 atm pressure and temperature –65 °C as it is heated up to room temperature at constant pressure.
A ‘thermacole’ icebox is a cheap and 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 coefficient 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]
A metal block of heat capacity 80 J°C−1 placed in a room at 20°C is heated electrically. The heater is switched off when the temperature reaches 30°C. The temperature of the block rises at the rate of 2°C s−1 just after the heater is switched on and falls at the rate of 0.2°C s−1 just after the heater is switched off. Assume Newton's law of cooling to hold.
- Find the power of the heater.
- Find the power radiated by the block just after the heater is switched off.
- Find the power radiated by the block when the temperature of the block is 25°C.
- Assuming that the power radiated at 25°C represents the average value in the heating process, find the time for which the heater was kept on.
Answer the following question based on the P-T phase diagram of carbon dioxide:
At what temperature and pressure can the solid, liquid and vapour phases of CO2 co-exist in equilibrium?
Answer the following question based on the P-T phase diagram of carbon dioxide:
What is the effect of decrease of pressure on the fusion and boiling point of CO2?
The radii of two copper spheres are in the ratio 1 : 3 and their temperatures are in the ratio 9 : 1. The ratio of heat content in them will be:
Mark the correct options:
- A system X is in thermal equilibrium with Y but not with Z. System Y and Z may be in thermal equilibrium with each other.
- A system X is in thermal equilibrium with Y but not with Z. Systems Y and Z are not in thermal equilibrium with each other.
- A system X is neither in thermal equilibrium with Y nor with Z. The systems Y and Z must be in thermal equilibrium with each other.
- A system X is neither in thermal equilibrium with Y nor with Z. The system Y and Z may be in thermal equilibrium with each other.
Relation between heat Q, mass mmm, and specific latent heat L ______.
Why does water stay at 100°C while boiling?
In a heating curve of ice and water, which part represents the latent heat of fusion?
Which statement best explains why the temperature of boiling water remains constant at 100°C until all the water has changed to steam (at 1 atm)?
For 1 kg of water, which phase change requires more energy?
