chemistry

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Relationship between the pressure and volume of helium gas at a constant temperature of 298K. Volume was changed by moving a piston & following data was obtained:
Vol (L) Pressure (atm)
5 10.229
10 4.749
15 3.198
20 2.381
30 1.665
50 0.98
75 0.655
100 0.47

1. what would be the pressure of the helium gas be if the volume of the cylinder would be changed to 40.0L?
I got 0.611 atm, is that right?
2. I have no clue how to begin this one so please help! since you are aware that for an ideal gas P=nRT/V, the relationship of P vs 1/V is expected to be a straight line. Recalculate the data and plot the graph of P vs. 1/V. Fit the best straight line through the points.

• chemistry - ,

I don't get that answer for #1. I calculated k from PV = k for each of the eight points shown in your post. Then I averaged the eight to find an avg number for k. Then PV = k; therefore, P=k/v, substituted the avg for k and 40 into that equation and calculated p. I obtained something like 1.2 or so but you should confirm that.
For #2, use a piece of graph paper, set up a scale for P and 1/V and the x and y axes, plot the data, and draw the best straight line through all the points.