On this page, the student begins to calculate some of the values that will be needed to determine the molecular weight of the unknown gas.

Again note how everything is clearly labeled.  However, the student does forget about significant figures when calculating the volumne of the 2 liter bottles.   The proper answer for bottle #49 is 2066.9 mL not 2066.856 mL.

At the bottom of the page there are a couple of minor mistakes.  Even though the 'Mr. Plot' software reported the intercept from the graph to be 56.59927,  the proper number of significant figures would be 56.6.  Secondly, a number without a unit is worthless.  So this should be written as 56.6 g.