Determination Of The Ideal Gas Constant And Molecular Weight Of A Gas

Determination of the Ideal Gas Constant "R" using Carbon Dioxide. (Report 3 digits for this exercise. No points will be deducted for significant digit errors.) (20 points)

Pressure/Volume Measurements. (Report 3 digits for this exercise. No points will be deducted for significant figure errors.) (20 points)

How do you explain the large percent error in the gas constant determination? There are both experimental and scientific factors involved. Include both.

While opening and closing the bag, a lot of dry ice leaves into the surrounding thereby changing the value of the initial mass we took. Also, the temperature of the bag changes since there is no proper insulation. Lastly, we assumed the gas to be ideal but in practice, no gas in the universe is ideal. All these factors lead to large percentage error in the calculation of Gas Constant.

If some water remained on the lighter at the time of the second weighing (after collecting the gas), how would this affect your determination of molecular weight? Be specific. Show a sample calculation to clarify your answer.

Mater remaining on the lighter will increase the measured final mass of butane. Let us assume the water droplets weigh 2 gm, then,

Initial mass = 12.6293 g

Final Mass = 14.7084 g

Mass of butane gas = 2.0791 g

Volume of gas = 35.10 mL

Using ideal gas equation : PV = nRT

(100471.75)(0.0000351) = ( )(8.314)(297.15)

M = 1456.5 g/mol

As can be observed above, just because of the presence of water droplets on the bag surface, the molecular mass of butane which is expected to be 52 g/mol is coming out as 1456.5 g/mol. Hence, before measurement of the mass, water droplets must be cleaned and dried.

Since, PV = constant in the measurements, therefore, Boyle’s Law is confirmed by the results of part-3.