Question
Read the passage given below and answer the following questions from (i) to (v).
First complete data on pressure-volume-Temperature relations of a substance in bothGaseous and liquid state was obtained byThomas Andrews on Carbon dioxide. He plottedlsotherms of carbon dioxide at variousTemperatures.
Later on it was found That real gases behave in the same manner asCarbon dioxide. Andrews noticed that at highTemperatures isotherms look like that of anldeal gas and the gas cannot be liquified even atVery high pressure. As the temperature isLowered, shape of the curve changes and dataShow considerable deviation from idealBehaviour. At $30.98^{\circ} C$ carbon dioxide remainsGas upto 73 atmospheric pressure. At 73 atmospheric pressure, liquidCarbon dioxide appears for the first time. TheTemperature $30.98^{\circ} C$ is called criticalTemperature (TC) of carbon dioxide. This is theHighest temperature at which liquid carbonDioxide is observed. Above this temperature itls gas. Volume of one mole of the gas at criticalTemperature is called critical volume $\left( V _{ c }\right)$ andPressure at this temperature is called criticalPressure (pc). The critical temperature, pressureand volume are called critical constants. A gasBelow the critical temperature can be liquifiedBy applying pressure, and is called vapour ofThe substance. Carbon dioxide gas below itsCritical temperature is called carbon dioxideVapour.
Intermolecular forces are stronger in liquidState than in gaseous state. Molecules in liquidsAre so close that there is very little empty space between them and under normal conditionsLiquids are denser than gases.Molecules of liquids are held together byAttractive intermolecular forces. Liquids haveDefinite volume because molecules do notSeparate from each other. However, moleculesOf liquids can move past one another freely, Therefore, liquids can flow, can be poured andCan assume the shape of the container in whichThese are stored. If an evacuated container is partially filled withA liquid, a portion of liquid evaporates to fillthe remaining volume of the container withVapour. Initially the liquid evaporates andPressure exerted by vapours on the walls of The container (vapour pressure) increases. AfterSome time it becomes constant, an equilibriumls established between liquid phase andVapour phase. Vapour pressure at this stagels known as equilibrium vapour pressure orSaturated vapour pressure.. Since process ofVapourisation is temperature dependent; the Temperature must be mentioned whilereporting the vapour pressure of a liquid.
When a liquid is heated in an open vessel,The liquid vapourises from the surface. At theTemperature at which vapour pressure of theLiquid becomes equal to the external pressure,Vapourisation can occur throughout the bulkOf the liquid and vapours expand freely intoThe surroundings. The condition of freeVapourisation throughout the liquid is calledBoiling. The temperature at which vapourPressure of liquid is equal to the externalPressure is called boiling temperature at thatPressure. At 1 atm pressure boilingTemperature is called normal boiling point.If pressure is 1 bar then the boiling point isCalled standard boiling point of the liquid. Standard boiling point of the liquid is slightlyLower than the normal boiling point because 1 bar pressure is slightly less than 1 atmPressure . The normal boiling point of water is $100^{\circ} C (373 K)$, its standard boiling point is $99.6^{\circ} C (372.6 K)$.At high altitudes atmospheric pressure isLow. Therefore liquids at high altitudes boil atLower temperatures in comparison to that atSea level. Since water boils at low temperatureOn hills, the pressure cooker is used forCooking food. In hospitals surgical instrumentsAre sterilized in autoclaves in which boilingPoint of water is increased by increasing thePressure above the atmospheric pressure byUsing a weight covering the vent.Boiling does not occur when liquid isHeated in a closed vessel. On heatingContinuously vapour pressure increases.
AtFirst a clear boundary is visible between liquidAnd vapour phase because liquid is more denseThan vapour. As the temperature increases more and more molecules go to vapour phaseAnd density of vapours rises. At the same timeLiquid becomes less dense. It expands becauseMolecules move apart. When density of liquidAnd vapours becomes the same; the clearBoundary between liquid and vapoursDisappears. This temperature is called critical Temperature.
First complete data on pressure-volume-Temperature relations of a substance in bothGaseous and liquid state was obtained byThomas Andrews on Carbon dioxide. He plottedlsotherms of carbon dioxide at variousTemperatures.
Later on it was found That real gases behave in the same manner asCarbon dioxide. Andrews noticed that at highTemperatures isotherms look like that of anldeal gas and the gas cannot be liquified even atVery high pressure. As the temperature isLowered, shape of the curve changes and dataShow considerable deviation from idealBehaviour. At $30.98^{\circ} C$ carbon dioxide remainsGas upto 73 atmospheric pressure. At 73 atmospheric pressure, liquidCarbon dioxide appears for the first time. TheTemperature $30.98^{\circ} C$ is called criticalTemperature (TC) of carbon dioxide. This is theHighest temperature at which liquid carbonDioxide is observed. Above this temperature itls gas. Volume of one mole of the gas at criticalTemperature is called critical volume $\left( V _{ c }\right)$ andPressure at this temperature is called criticalPressure (pc). The critical temperature, pressureand volume are called critical constants. A gasBelow the critical temperature can be liquifiedBy applying pressure, and is called vapour ofThe substance. Carbon dioxide gas below itsCritical temperature is called carbon dioxideVapour.
Intermolecular forces are stronger in liquidState than in gaseous state. Molecules in liquidsAre so close that there is very little empty space between them and under normal conditionsLiquids are denser than gases.Molecules of liquids are held together byAttractive intermolecular forces. Liquids haveDefinite volume because molecules do notSeparate from each other. However, moleculesOf liquids can move past one another freely, Therefore, liquids can flow, can be poured andCan assume the shape of the container in whichThese are stored. If an evacuated container is partially filled withA liquid, a portion of liquid evaporates to fillthe remaining volume of the container withVapour. Initially the liquid evaporates andPressure exerted by vapours on the walls of The container (vapour pressure) increases. AfterSome time it becomes constant, an equilibriumls established between liquid phase andVapour phase. Vapour pressure at this stagels known as equilibrium vapour pressure orSaturated vapour pressure.. Since process ofVapourisation is temperature dependent; the Temperature must be mentioned whilereporting the vapour pressure of a liquid.
When a liquid is heated in an open vessel,The liquid vapourises from the surface. At theTemperature at which vapour pressure of theLiquid becomes equal to the external pressure,Vapourisation can occur throughout the bulkOf the liquid and vapours expand freely intoThe surroundings. The condition of freeVapourisation throughout the liquid is calledBoiling. The temperature at which vapourPressure of liquid is equal to the externalPressure is called boiling temperature at thatPressure. At 1 atm pressure boilingTemperature is called normal boiling point.If pressure is 1 bar then the boiling point isCalled standard boiling point of the liquid. Standard boiling point of the liquid is slightlyLower than the normal boiling point because 1 bar pressure is slightly less than 1 atmPressure . The normal boiling point of water is $100^{\circ} C (373 K)$, its standard boiling point is $99.6^{\circ} C (372.6 K)$.At high altitudes atmospheric pressure isLow. Therefore liquids at high altitudes boil atLower temperatures in comparison to that atSea level. Since water boils at low temperatureOn hills, the pressure cooker is used forCooking food. In hospitals surgical instrumentsAre sterilized in autoclaves in which boilingPoint of water is increased by increasing thePressure above the atmospheric pressure byUsing a weight covering the vent.Boiling does not occur when liquid isHeated in a closed vessel. On heatingContinuously vapour pressure increases.
AtFirst a clear boundary is visible between liquidAnd vapour phase because liquid is more denseThan vapour. As the temperature increases more and more molecules go to vapour phaseAnd density of vapours rises. At the same timeLiquid becomes less dense. It expands becauseMolecules move apart. When density of liquidAnd vapours becomes the same; the clearBoundary between liquid and vapoursDisappears. This temperature is called critical Temperature.
- First complete data on Pressure-Volume-Temperature relations of a substance in both Gaseous and liquid state was obtained by:
- Thomas Andrews
- Fritz London
- Robert Boyle
- Joseph Lewis Gay Lussac
- Critical Temperature (TC) of carbon dioxide is.....
- $24^\circ C$
- $30.8^\circ C$
- $56^\circ C$
- $29^\circ C$
- The condition of free Vapourisation throughout the liquid is called …
- Evaporation
- Melting
- Boiling
- None of above
- Standard boiling point of Water is....
- $100^\circ C$
- $3^\circ C$
- $105^\circ C$
- $99.6^\circ C$
- Boundary between liquid and vapours Disappears,This temperature is called …
- Critical temperature
- Absolute temperature
- Normal temperature
- Boiling temperature
