In one experiment, a dry sample of an unknown
Gas was collected. Its volume at 745 mm Hg and
63.0 oC was 815.5 mL. How many moles of this gas
Was obtained?

a. 0.0290 moles b. 2.90 moles
c. 29.0 moles d. 2310 moles
e. none of the above.

Test q I got wrong, WHY

In one experiment, a dry sample of an unknown gas was collected. Its volume at 745 mm Hg and 63.0 oC was 815.5 mL. How many moles of this gas was obtained?

a. 0.0290 moles b. 2.90 moles
c. 29.0 moles d. 2310 moles
e. none of the above.



T = 63.0 C = 336.15 K
V = 815.5 mL = 0.8155 L
P = 745 mm Hg = 745 Torr

PV=nRT

R is 62.363 67 L Torr  K−1 mol−1. Note I picked the constant in these units because those are the units I have for my other variables. R is available in many different units. I'm not showing the units in the following equation, but I could -- and all the units except moles would cancel.

745 \times 0.8155 = n \times 62.36367 \times 336.15

n = 0.0290