What is the pressure in millimeters of mercury of 0.0130 mol of helium gas with a volume of 208 mL at a temperature of 30 C?

1 Answer
Dec 5, 2016

We use the ideal gas equation to give an approximate pressure of 130*mm*Hg130mmHg

Explanation:

From the Ideal Gas equation P=(nRT)/VP=nRTV

=(0.0130*cancel(mol)xx0.0821*cancelL*atm*cancel(K^-1*mol^-1)xx303*cancel(K))/(208*cancel(mL)xx10^-3cancelL*cancel(mL^-1))

= 0.17*atm

Now we were asked to quote the pressure in mm*Hg. It is a fact that 1 "atmosphere" will support a column of mercury 760*mm high. This property is a handy laboratory measurement because you can measure small pressure differences by the difference in heights of mercury columns, relative to the daily atmospheric pressure.

"Pressure "mm*Hg-=0.17*atmxx760*mm*Hg*atm^-1=??mm*Hg.