Question

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?

Answer 1

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

Explanation:

From the Ideal Gas equation `P=(nRT)/V`

`=(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.`