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Question
Answer the following questions based on the P–T phase diagram of CO2:
CO2 is heated to a temperature 70 °C and compressed isothermally. What changes in its properties do you expect to observe?
Solution 1
It departs from ideal gas behaviour as pressure increases.
Explanation:
If CO2 is heated to 70°C and compressed isothermally, then it will not exhibit any transition to the liquid state. This is because 70°C is higher than the critical temperature of CO2. It will remain in the vapour state, but will depart from its ideal behaviour as pressure increases
Solution 2
Above 31.1°C, the gas cannot be liquefied. Therefore, on being compressed isothermally at 70°C, there will be no transition to the liquid region. However, the gas will depart, more and more from its perfect gas behaviour with the increase in pressure.
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