VARIATION OF SATURATED VAPOUR PRESSURE (S.V.P) OR WATER WITH TEMPERATURE USING A CAPILLARY TUBE WITH A WATER INDEX.

AIM: to determine the variation of saturated vapour pressure (s.v.p) or water with temperature using a capillary tube with a water index.

APPARATUS: Thick walled capillary tube closed at one end, millimeter scale(ruller),rubber bands, thermometer, stirrer.

DIAGRAM:

THEORY: Throughout the heating experiment,the air below the water index is saturated and is at a constant pressure atmosphere.at any temperature the partial pressure of air is

   p-px

 where p=atmospheric pressure.

            px=s.v.p at the temperature                (X=1or 2).

  let p1 and p2 be the s.v.p of water at the temperatures t1 and t2 respectively and v1 and v2 the corresponding volumes of air at the temperatures.

  PV/T=K(constant)

  Then (P-P1)V1/273+t1=(P-P2)V2/273+t2

Since the volume of the trapped air is proportional to the length, equation can be written as

  (P-P1)L1/273+t1=(P-P2)L2/273+t2

PROCEDURE:

The capillary tubing was warmed gently over to burden burner(while rotating to avoid cracking),and the open end was dipped into cold water.a thread of water that entered the capillary tubing was displaced to about the middle by tapping the capillary was attached to the ruler using the rubber bands and was placed in a beaker that had water in it.

   The open end of the tubing was opened to the air and the water was heated slowly and stirred regularly, while the length of the trapped moist air was measured at temperature intervals of about 5°C between 25°C and 60°C.heating was then stopped when the water index had reached the top of the tubing.the source of heat was removed and the apparatus was allowed to cool,the measurement of the length of the moist air at the same temperature was repeated.

TABLE OF VALUES AND CALCULATIONS

Here is an easy one we left for you. Make P the subject of formula. That is the answer to the question

PRECAUTION OF VARIATION OF SATURATED VAPOUR PRESSURE (S.V.P) OR WATER WITH TEMPERATURE USING A CAPILLARY TUBE WITH A WATER INDEX.

1. The capillary tube was rotated during heating to prevent cracking.
2. The water bath was stirred regularly during heating to prevent uneven spread of temperature.
3. Thermometer with calibration from 0°C to 100°C was used to prevent inaccurate reading of temperature.

 CONCLUSION:The unknown resistance X for the thin and thick wires respectively are 0.48 and 3.05ohms and the specific resistance (resistivity) for the thin wire is greater than that of the thick.
PRECAUTION:
1. it was ensured that the wire used was uniform,the Jockey was touched lightly by the wire.
2. it was ensured that before seeking the null point the key was closed before contact was made at D to avoid deflection due to the inductor effect.
3. it was ensured that small current was passed through the galvanometer G to avoid damage.