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EXPERIMENT NO.3:
TO DETERMINE THE BOILING POINT Of A GIVEN LIQUID
APPARATUS:
- Beaker
- Thermometer
- Test tube
- Capillary tube
- Tripod stand
- Wire gauze
- Spirit lamp (Bunsen burner)
- Stirrer
- Rubber band
CHEMICALS:
- Ethyl Alcohol (carbon tetra-chloride and paraffin liquid or any given liquid)
- Water
THEORY:
Temperature A which the vapour pressure of liquid becomes equal to the atmosphere pressure is called boiling point.
The boiling point is a physical property of a substance. It can be defined in terms of the vapour pressure of the solvent. It is the temperature at which the vapour pressure of the liquid Of solvent in a solution is equal to external pressure (i.e. atmospheric pressure). This means liquids can boil at almost any temperature if the external pressure is adjusted. When the pressure on a liquid is increased the boiling point goes up, and if the pressure on a liquid is reduced so it lowers the boiling point. Boiling point is also a characteristic constant, a pure liquid boils at a higher temperature whether the liquid contains a non-volatile or volatile impurities.
1st. METHOD:
- Seal a small capillary glass tube at one end.
- Take a small quantity (2 ml) of ethyl alcohol in a small test tube.
- Insert the sealed capillary tube upside down into the small test tube, inside the ethyl alcohol.
- Tie the small test tube with a thermometer in such a way that its lower encl remain near the bulb.
- Suspend the thermometer on a clamp.
- Take it beaker half filled with water and place it over a wire gauze which is placed over a tripod stand.
- Lower the thermometer along with the small test tube into the water without touching the wall base by adjusting the clamp on the stand.
- Fix the clamp.
- Now slowly heat the beaker with a Bunsen burner or spirit lamp with constant stirring the water.
- When bubbles come out rapidly from the lower end of capillary tube, the temperature on thermometer is noted.
- Stop heating by removing the burner or spirit lamp.
2nd. METHOD:
- Seal a small capillary glass tube at one end.
- Take a small quantity (2 ml.) of ethyl alcohol in a small test tube.
- Insert the sealed capillary tube upside down into the test tube, inside the ethyl alcohol.
- Clamp the test tube with iron stand and put it into the beaker which contains water and placed on a tripod stand such that ethyl alcohol remain In water.
- Now clamp a thermometer with an iron stand and dip it into the ethyl alcohol in such a way that its bulb remain in ethyl alcohol.
- Now slowly heat the beaker with a Bunsen burner or spirit lamp with constant stirring the water.
- When bubbles come out rapidly from the lower end of capillary tube, the temperature on thermometer is noted.
- Stop heating by removing the burner or spirit lamp.
OBSERVATIONS:
Boiling point of ethyl alcohol is 78 °C.
RESULT:
Boiling point of given sample of ethyl alcohol (C2H5OH) is 78 °C.
PRECAUTIONS:
- Water should be heated gently.
- Stirring should be constant.
- Bulb of thermometer should not touch the walls and base of the beaker.
- Too much or too little sample can be a cause of error.
- Adjust flame size so that the temperature rises no more than 2-3 degree per minute.
- A sample is only used once for boiling point determination.
- The graduated side of thermometer should face you.
Note: Result may be vary depending on the purification of ethyl alcohol.
Special Thanks to Sir Sajjad Akber Chandio
Thanks its like pond for a thirsty man In desert.
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