EXPERIMENT 5 IDEAL GAS LAW : CHARLES'S LAW PDF

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EXPERIMENT 5 IDEAL GAS LAW : CHARLES’S LAW OBJECTIVE: Upon completion of the experiment, students should be able: 1. To measure the volume of a fixed quantity of air as the temperature changes at constant pressure. 2. To verify Charles’s Law. INTRODUCTION: Jacques Charles observed that for a fixed q...

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EXPERIMENT 5 IDEAL GAS LAW : CHARLES’S LAW OBJECTIVE: Upon completion of the experiment, students should be able: 1. To measure the volume of a fixed quantity of air as the temperature changes at constant pressure. 2. To verify Charles’s Law. INTRODUCTION: Jacques Charles observed that for a fixed quantity of gas, the volume at constant pressure changes when temperature changes: the volume increases (V↑) when the temperature increases (T↑); the volume decreases (V↓) when the temperature decreases (T↓). Although first described by Charles in 1787, it was not until 1802 that Joseph Gay-Lussac expressed the relationship mathematically. Charles’s Law states that when the pressure is held constant, the volume of a fixed mass of ideal gas is in direct proportion to the temperature in degrees Kelvin. Charles’s Law can be written mathematically as follows: 1. V = k * T or V / T = k

Where V is the volume of the gas, T is the temperature in degrees Kelvin, and k is a constant that depends on the pressure and amount of gas. The direct relationship is clear by looking at the equations. If a sample of gas at a fixed pressure has its temperature doubled, the volume in turn is doubled. Conversely, decreasing the temperature by one half brings about a decrease in volume by onehalf.

The law applies, for a given pressure and quantity of gas, at all sets of conditions. Thus for two sets of T and V, the following can be written:

2. (V1 / T1 = V2 / T2) or (V1T1 = V2T2) or (V1T1 / V2T2 = 1)

Where at constant pressure, V1 and T1 refer to the set of conditions at the beginning of the experiment, and V2 and T2 refer to the set of conditions at the end of the experiment. Charles’s Law can be illustrated by a hot-air balloon. The material that the balloon is made from is stretchable, so the pressure of the air inside is constant. As the air inside is heated (T↑), the volume of the air increases (expands; V↑) and the balloon fills out. With the mass the same but the volume larger, the density decreases. Since the air inside is less dense than the air outside, the balloon rises. This experiment determines the volume of a sample of air when measured at two different temperatures with the pressure held constant.

APPARATUS NEEDED: 1. Boiling stones. 2. Hot plate. 3. Glass tubing (6 to 8 cm length; 7-mm OD). 4. 2 Erlenmeyer flasks (250 mL). 5. 2 Beakers (800 mL). 6. Retort stand. 7. Marking pencil. 8. One-hole rubber stopper (size no. 6). 9. Rubber tubing (2 ft. length). 10. Thermometer (110°C).

PROCEDURE:

1. Use a clean and dry 250 mL Erlenmeyer flask (Flask no. 1). Fit the flask with a prepared stopper assembly, consisting of a no. 6 one-hole rubber stopper which has a 5-cm to 8-cm length of glass tubing inserted through the hole. If an assembly needs to be constructed, use the following procedure: a. Select a sharpened brass cork borer with a diameter that just allows the glass tubing to pass through it easily. b. Lubricate the outside of the cork borer with glycerine and push it through the rubber stopper from the bottom. c. Once the cork borer is through the stopper, pass the glass tubing through the cork borer so that the tubing is flush with the bottom of the stopper. d. Grasp the tubing and the stopper with one hand to hold these two pieces stationary; with the other hand carefully remove the borer. The glass tubing stays in the stopper. (Check to be certain that the end of the glass tubing is flush with the bottom of the rubber stopper.) 2. Mark the position of the bottom of the rubber stopper on Flask no. 1 with a marking pencil. Connect rubber tubing to the glass tubing. 3. Place 300 mL of water and three (3) boiling stones in an 800 mL beaker. Place the beaker on a hot plate and heat to boiling. Keep the water at a gentle boil. Record the temperature of the boiling water. 4. Prepare an ice water bath using a second 800 mL beaker half-filled with a mixture of ice and water. Record the temperature of the bath. Set aside for use in step no. 8. 5. Put about 200 mL of water into a second 250 mL Erlenmeyer flask (Flask no. 2) and place the end of the rubber tubing into the water. Make sure that the end of the rubber tubing reaches to the bottom of the flask and stays submerged at all times. (You may wish to hold it in place with a clamp attached to a ring stand.) 6. Lower the flask as far as it will submerge into the boiling water. Secure onto the ring stand (Figure. 5.1). Adjust the water level in the beaker to cover as much of the Erlenmeyer flask as possible.

7. Boil gently for 5 min. Air bubbles should emerge from the rubber tubing submerged in Flask no. 2. Add water to the beaker if boiling causes the water level to go down. 8. When bubbles no longer emerge from the end of the submerged tubing (after 5 min.), carefully lift Flask no. 1 from the boiling water bath and quickly place it into the ice water bath. Record what you observe happening as Flask no. 1 cools. Be sure to keep the end of the rubber tubing always submerged in the water in Flask no. 2. 9. When no more water is drawn into Flask no. 1, raise the flask until the level of water inside the flask is at the same height as the water in the ice-water bath. Then remove the stopper from the Flask no. 1. 10. Take a measuring cylinder and measure the water in Flask no. 1. Record the volume to the nearest 0.1mL. 11. Determine the volume of Erlenmeyer Flask no. 1 as follows: a. First, fill it with water to the level marked by the marking pencil. Insert the stopper with the glass tubing into the flask to be sure the bottom of the stopper touches the water with no air space present. Adjust the water level if necessary. b. Remove the stopper and measure the volume of the water in the flask by pouring it into a measuring cylinder. c. The total volume of water should be measured to the nearest 0.1 mL. Record this value. 12. Do the calculations to verify Charles’s Law.

DATA: Temperature, boiling water (T2)

98 °c 371 K

Observation as Flask no. 1 cools (Procedure No. 8)

Temperature, ice water (T1)

5 °c 278 K

Volume of water sucked into Flask no. 1

44 mL

(Vw)

Volume of air at the temperature of

200 mL

boiling water (V2) (Procedure No. 11)

Volume of the air at the temperature of

156 mL

ice water (V1)

(V1 = V2 - Vw) Verify Charles’s Law from experiment

(200 × 5) / (156 × 98)

(V2 × T1) / (V1 × T2)

(1000) / (15288) = 0.0654

Percent deviation from Charles’s Law

(1.00 – 0.0654) / (1.00) × (100)

% =[1.00 – (Data 8)] / (1.00) × (100)=

= 93.46%

DISCUSSION: 1. Indicate whether the following statements about Charles’s Law are true (T) or false (F): a) As temperature doubles from 10°C to 20°C, the volume doubles. = True b) As the volume decreases by one-half, the temperature decreases by one-half. = True c) Volume is inversely related to the temperature at constant pressure. = False (Volume directly proportional to Temperature) 2. In this experiment, if a student assumed the volume of the 250 mL Erlenmeyer flask to be 250 mL without actually measuring the volume, how would this assumption affect the deviation from Charles’s Law results? = The results are inaccurate because the student did not measure the volume correctly. 3. In step no. 9 of the Procedure, flask no. 1 is raised until the level of water inside the flask is at the same height as the water in the ice-water bath. Why was this done? = To equalize the pressure in the flask, the water level inside the flask is adjusted to the level of the water in the ice bath by raising or lowering the flask. 4. How you conclude the collecting volume in this experiment is related to the temperature at constant pressure? = My conclusion is that when the temperature increase the volume also increase and when temperature decrease the volume also decrease.

CONCLUSION: The purpose of this lab was to see the relationship of temperature and volume. Charles’s Law is a law which explains this correlation. First of all, there could have been an error in the timing in allowing the flask to cool. If the lab was incorrectly timed then the correct temperatures may not have been achieved. There was also a possibility of error in terms of not maintaining the time of boiling for long enough as well. If the boiling was done for too long and the cooling was not done long enough then there was high probability that the results may have been error. Another possible error is that the pinch clamp was not correctly secured around the flask. If the pinch clamp is not secured properly than water cannot be kept out of the flask and there is no correct volume. Another mistake that could cause problems is if the flask is not raised correctly when submerged in water. When the flask is raised this equalizes the pressure. If this is not done correctly than the pressure is not equalized and Charles Law no longer applies.

REFERENCE: 1. https://en.wikipedia.org/wiki/Charles%27s_law 2. http://chemistry.bd.psu.edu/jircitano/gases.html 3. http://www.chemguide.co.uk/physical/kt/otherlaws.html 4. https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Physica l_Properties_of_Matter/States_of_Matter/Properties_of_Gases/Gas_Laws/Th e_Ideal_Gas_Law 5. https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved= 0ahUKEwixnqjZvYbWAhVFpY8KHf3dA_kQFgglMAA&url=http%3A%2F%2Fs wc2.hccs.edu%2Fpahlavan%2Fintro_labs%2FExp_16_Charles_Law_Volume _and_Temperature.pdf&usg=AFQjCNHnqUretp88U7zAYSMkqRUQCqUTgw 6. http://www.passmyexams.co.uk/GCSE/physics/volume-temperaturerelationship-of-gas-Charles-law.html...