lab gaslaws

7/31/2019 Lab Gaslaws

1/4


2/4

Analysis: Using Excel, plot temperature (x-axis) versus pressure (y-axis). Make sure there is enough room

in the graph to be able to extrapolate the graph back at least a hundred degrees. In other words, make the x-axis range from 300C to 100C. Usual rules apply; give the graph a goodtitle, and axes labels (with units).

Use the Add Trendline function to draw a best-fit line using a linear regression algorithm, andgive the equation for the line.

Part 2 Molar Mass of CO 2 Introduction: The ideal gas law gives the relationship between the characteristic properties of a gas:PV = nRT where P is the gas pressure, V is the gas volume, n is the amount (in this case, moles) of gasand T is the gas temperature.

Of course, the number of moles of a gas is equal to the mass of a given amount of gas divided bythe gass molar mass. To put it another way, the molar mass ( MM) of a gas is equal to the mass of agiven amount of gas divided by the number of moles in that amount of gas.

Symbolically, MM = m/n, where m is the mass of a given amount of gas.

The ideal gas law can be algebraically rearranged so that it is solved for the number of moles of gas:n = PV/RT.

Combining the previous two equations:

MM = mRT/PV

In other words, you can find the molar mass of a pure gaseous substance by measuring the mass ofgas in a certain space, the temperature and pressure of the gas and the volume of the space. Recallthat R is the ideal gas constant, whose value can be found in nearly any reference.

In this experiment, you will fill a flask full of carbon dioxide, weigh it and determine the volume,pressure and temperature of the carbon dioxide and calculate the molar mass of carbon dioxideusing the equation above.

One complication is that weighing the carbon dioxide gas is hard; you cant simply tare the balanceand add carbon dioxide. You will need to figure out the mass of the air inside the flask and subtractthat off of the mass of the flask in order to get just what the flask weighs.

Materials 250 mL Erlenmeyer flask Rubber stopper Electronic balance Thermometer

Barometer (attached to classroom wall) 100 mL graduated cylinder Small piece of dry ice

SafetyDry ice sublimes at 78.5C; that is the temperature of the dry ice in this experiment. It will cause burns

upon prolonged or repeated exposure to bare skin, so do not pick up the dry ice with your bare hands;use a paper towel. Carbon dioxide and water are not considered hazardous, so all fluids can bepoured down the sink.


3/4


4/4

Post-lab AssignmentPart 1:

Submit your data table and Excel graph. Clearly show your final result (the value of absolute zero in C?)

Respond in detail to the following questions:1. Discuss which Gas Law the linearity of your graph confirms?

2. The gas inside the ball of the pressure-measuring device is air. What assumption did you makeabout the behavior of air as you extrapolated the data to absolute zero? Why did you have to makethis assumption? How good of an assumption is it?

Part 2 Submit your data, sample calculations and results from both your data and the class data Write an Abstract

lab gaslaws

Documents