The volume of the air sample at the high temperature, when the sample is cooled to the low enrapture and becomes. All of these measurements are made directly. The experimental data is then used to verify Charleston by two methods: 1. The experimental volume (V””o) measured at the low temperature is compared to the VI predicted by Charles’ law where Y(t erotic at)- ) 2. The WET ratios for the air sample measured at both the high and the low temperatures are compared, Charleston predicts that these ratios will be equal.
Pressure Considerations The relationship between temperature and volume defined by Charles’ law is valid Only if the pressure is the same When the volume s measured at each temperature. That is not the case in this experiment. 1. The volume, Vs…… Of air at the higher temperature, TTS is measured at atmospheric pressure’ in a dry Erlenmeyer flask. The air is assumed to be dry and the pres. NRC” is obtained from a barometer. 2. The experimental air volume, at the lower temperature, Tip, is measured. Over water.
This volume is saturated with water vapor that contributes to the total pressure in the flask. Therefore, the experimental volume must be corrected to the volume of dry Ankara atmospheric pressure. This is done using Bole’s law as follows: a. The partial pressure of the dry air, Poor is calculated by subtracting the vapor pressure of water from atmospheric pressure: P. R–From-POP b. The volume that this dry air would occupy at Purr,’IIS then calculated using the Bole’s law equation: = =Sift (vivo) PROCEDURE Wear protective glasses.
NOTE: It is essential that the Erlenmeyer flask and rubber stopper assembled as dry as possible order to obtain reproducibility’s_ Dry a 125 ml Erlenmeyer flask by gently heating the entire outer surface with a burner flame. Care must be used in heating to avoid breaking the flask. Fifth flask is wet, first Wipe the inner and outer surfaces with a towel to remove nearly all the water. Then, holding the flask With a test tube holder, gently heat the entire flask. Avoid placing the flask directly in the flame. Allow to cool.
While the flask is cooling select a I-hole rubber stopper to fit the flask and insert a b CM piece Of glass tubing into the stopper so that the end of the tubing is flush with the bottom of the stopwatches a 3 CM piece of reprobating the glass tubing (see Figure 19. 1-). Insert (wax pencil) the distance that it is inserted. Clamp the the stopper onto the flask and mark flask so that it is submerged as far as possible in water contained in a 400 ml beaker (without the flask touching the bottom of the beaker) (see Figure 19. 2). Heat the water to boiling.
Keep the flask in the gently boiling water tort at least 8 minutes to allow the air in the atlas to attain the temperature of the boiling water. Add water as needed to maintain the water level in the beaker. Read and record the temperature of the boiling water. While the flask is still in the boiling water, seal it by clamping the rubber tubing tightly with a screw clamp. Remove the flask from the hot water and submerge it in a an of cold water, keeping the top down at all times to avoid losing aim Remove the screw clamp, letting the cold water flow into the flask.
Keep the flask totally submerged for about 6 minutes to allow the flask and contents to attain the temperature of the water. Read and record the temperature of the water in the pan. Figure 19. I Rubber stopper assembly Figure 192 Heating the flask (and air) in boiling water In order to equalize the pressure inside the flask with that of the atmosphere, bring the water level in the flask to the same level as the water in the pan by raising or lowering the flask (see Figure 19. ). With the water levels equal, pinch the rubber tubing to close the flask.
Remove the flask from the water and set it down on the laboratory bench. Using a graduated cylinder carefully measure and record the volume of liquid in the flask, Repeat the entire experiment, use the same flask and flame dry again; make sure that the rubber stopper assembly is thoroughly dried inside and outside, After the second trial fill the flask to the brim with water and insert the stopper assembly to the mark, letting the glass and rubber furl to the top and overflows Measure the volume of water in the flask.
Since this volume is the total volume of the flask, record it as the volume of air at the higher temperature. Because the same flask is used in both trials. It is necessary to make this measurement only once. Figure 19. 3 Equalizing the pressure in the flask. The water level inside the flask is adjusted to the level Of the water in the pan by raising or lowering the flask. NAME SECTION DATE REPORT PRESENTIMENT 19 Charleston INSTRUCTOR Data Table Tail 1 Temperature of boiling water, TTS Temperature of cold water, Tip Volume of water collected in flask (decrease volume due to cooling) -co CO.
K – co, -co, T? Ill 2 Volume of air at higher temperature, Vs….. (volume of flask measured only after Trial 2) Volume of wet air at lower temperature (volume of flask less volume of water Atmosphere pressure, reading) Vapor pressure of water at lower temperature, Poop (expanding 6) REPORT FOR EXPERIMENT 19 (continued) NAME CALCULATIONS: In the spaces below, show calculation setups for T? Ill 1 only.
Show answers for both trials in the boxes T bill I I, Corrected experimental volume of dry air at the lower temperature calculated from data obtained at the lower temperature. A) Pressure of dry air (App) T)IA (b) Corrected experimental volume Of dry air (lower temperature). 2 . Predicted volume of dry air at lower temperature Vs….. Calculated by Charles’ law from volume at higher temperature (VHF). Roth 3. Percentage error in verification of Charleston. Vivo – Vt vow terror = x lo FL 4. Comparison experimental/T ratios. Use dry of volumes obstreperousness’s. ) (b) ;nun = REPORT MEET 1 g (continued) ANAL 5 . On the graph paper provided, plot the volume- temperature values used in Calculation 4. Temperature data must be in co. Draw a straight line be,even he two plotted points and extrapolate (extend) the line so that it crosses the temperature axis. QUEUE ACTIONS ADD PROBLEMS 1 . (a) In the experiment, why are the water levels inside and outside the flask equalized before removing the flask from the cold water? B) When the water level is higher inside than outside the flask. Is the gas pressure in the flask higher than, lower than, or the same as, the atmospheric pressure? (specify which) 2. A L AS ml sample of dry air at 230″C is cooled to OIC”C at constant pressure, What volume will the dry air occupy at 100″C? 3. A 250 ml container of a gas is at CO’S_ At what temperature will the gas occupy a volume of 125 ml, the pressure remaining constant? 4 . (a) An open flask of air is cooled.
Answer the following: 1. Under which conditions, before or after cooling, does the flask contain more gas molecules? 2. Is the pressure in the flask at the lower temperature the same as, greater than, or less than the pressure in the flask before it was cooled? (b) An open flask of air is heated, stopper in the heated condition, and then allowed to cool back to mom temperature. Answer the following: 1. Does the flask notation the same, more, or fewer gas molecules now compared to before it was heated? 2. 5 the volume occupied by the gas in the flask approximately the same, greater, or less than before it was heated? 3. Is the pressure in the flask the same, greater, or less than before the flask was 4. DO any Of the above conditions explain Why water rushed into the flask at the lower temperature in the experiment? Amplify your answer. 5. On the graph you plotted, (a) At what temperature does the extrapolated line intersect the r. Axis? Co (b) At what temperature does Charleston predict that the extrapolated line should intersect the r-axis?