Purpose: To explore the gas laws. Equipment needed: Gas Laws Lab See each individual experiment Background: When molecul

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Purpose To Explore The Gas Laws Equipment Needed Gas Laws Lab See Each Individual Experiment Background When Molecul 1 (47.45 KiB) Viewed 77 times

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Purpose: To explore the gas laws. Equipment needed: Gas Laws Lab See each individual experiment Background: When molecules or atoms are in the gas phase, they tend to behave in a manner which is consistent with the Kinetic Molecular Theory. Such gases are termed Ideal Gases, and follow the mathematical relationship: PV=nRT where P-pressure (atm), V-volume (L), n number of moles of gas, T-temperature (K) and R-Ideal Gas Constant, 0.08206 L atm mol¹K¹ Since R is a constant, this equation can be rewritten as: PV nT for any gas which behaves ideally, for any combination of pressure, volume and number of moles of gas. Thus, the ideal gas law can be rewritten to compare two different sets of conditions, a form called the Combined Gas Law. -R = P.V₁ P₂V₂ n/T, n₂T₂ With the combined gas law, we can predict the effects of changing conditions on the properties of a gas. Pre-Laboratory Exercise: Prepare the lab notebook to collect data. You will transfer the answers to this document after the lab. In complete sentences in your lab notebook answer the following questions: 1. What is the effect of an increase in temperature on molecular velocity? 2. How does this change affect the force of the gas molecules collisions with the walls of the container? 3. What is the resultant change in pressure in a closed system that cannot expand? 4. What is the resultant volume change in a system that can expand and contract, but whose pressure is constant if you increase the temperature of the system?
Experiment 1: The relationship of volume and pressure (Demonstration) This experiment will allow us to examine how changes in volume affect the pressure of a gas in a container. 1) Circle the correct response: a) To increase the volume of a gas in a container we must [increase; decrease] the surface area of the container. b) There are [the same; fewer] number of molecules in the container when the volume of the container is changed. c) Pressure in force/area. As the volume of the gas increases then the area [increases; decreases] and so the pressure of the gas [increases; decreases]. 2) Write down the pressure in atmospheres and the volume in liters. Calculate volume for each data point and record your values in the table below: Pressure (atm) 1/volume (L¹) ● Volume (L) 3) Make a graph of pressure versus 1/V. Put pressure on the y-axis and 1/V on the x axis. Label your axis and title your graph and determine the trendline. The data should be a straight line. A straight line can be described by the equation y=mx+b where m is the slope and b is the intercept. In this case the slope, m, is equal to nRT and the intercept b will be approximately zero. Determine the slope either by hand or by computer. See the graphing lab for more details. Slope from equation of line from graph- • 4) Use Slope = nRT, where slope is the slope from the equation of the line on your graph, R=0.08206 L atm/mole K, T-room temperature (25°C) to calculate the number of moles (n) in the container.
Experiment 2 Equipment needed: I empty aluminum soda can 1 ice bath (plastic) filled with ice water I hot plate 1 pair crucible tongs 1 Thermometer Place the aluminum can on the hot plate. Pour a few mL of water into the can, and heat until the water boils (evidenced by a large quantity of steam evolving from the can). Lift the can off the plate using the crucible tongs and drop it upside down into the beaker of ice water. Record your observations below. In this experiment, volume is held constant because the walls of the container are rigid. The number of moles is held constant because the hole in the can is sealed when it is turned upside down and immersed in the water/ice bath. Temperature of the water in the ice bath Observations: 1. Calculations: Generic Col a. T₁ (in K) = b. T₂ (in K) - c. P₁ (in atm)- d. Pa calculated= e. Calculation for P₂ 2. What caused the change in the can's appearance? Explain your observations.
Experiment 3 Equipment needed: 1250 mL Erlenmeyer flask 1 balloon 1 ice bath 1 hot plate 1 Thermometer Place about 50 mL of water into the Erlenmeyer flask. Place the flask on the hot plate and bring it to a boil. Remove the flask from the hot plate and place the balloon over the top of the flask. Quickly plunge the flask into the ice bath. Temperature of the ice bath_ Observations: Questions: 3. Calculation T, (in K) = T₂ (in K)= V₁ (in mL) = V₂ calculated- Calculation for V₂ 4. What caused the change in the appearance of the balloon? Explain your observations. T