Chemistry Class-11: Chapter –5. States of Matter Part – 10

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Question: 51

The variation of vapour pressure of different liquids with temperature is shown in Fig. 5.6.

The variation of vapour pressure of different liquids with temperature

PV Curve

The variation of vapour pressure of different liquids with temperature

(i) Calculate graphically boiling points of liquids A and B.

(ii) If we take liquid C in a closed vessel and heat it continuously. At what temperature will it boil?

(iii) At high altitude, atmospheric pressure is low (say 60 mm Hg). At what temperature liquid D boils?

(iv) Pressure cooker is used for cooking food at hill station. Explain in terms of vapour pressure why is it so?

Answer:

(i) Boiling point of

(ii) Will not boil

(iii) Approximately

(iv) A liquid boils when vapour pressure becomes equal to the atmospheric pressure. Water boils at low temperature on hills because atmospheric pressure is low. Therefore even at low temperature vapour pressure becomes equal to atmospheric pressure.

Question: 52

Why does the boundary between liquid phase and gaseous phase disappear on heating a liquid up to critical temperature in a closed vessel? In this situation what will be the state of the substance?

Answer:

Question: 53.

Why does sharp glass edge become smooth on heating it up to its melting point in a flame? Explain which property of liquids is responsible for this phenomenon.

Answer:

Question: 54

Explain the term ‘laminar flow’. Is the velocity of molecules same in all the layers in laminar flow? Explain your answer.

Question: 55

Isotherms of carbon dioxide gas are shown in Fig. 5.7. Mark a path for changing gas into liquid such that only one phase (i.e., either a gas or a liquid) exists at any time during the change. Explain how the temperature, volume and pressure should be changed to carry out the change.

Isotherms of carbon dioxide gas

PV Curve

Isotherms of carbon dioxide gas

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