Question

In a gaseous mixture of a 2.0⋅L volume, at 755⋅mm Hg, and a temperature of 346⋅K, Pdinitrogen=355⋅mm⋅Hg. What are the molar quantities of helium and dinitrogen?

Answer 1

Explanation:

The idea here is that after all the ice sublimes, the balloon will contain

2.50 g

of gaseous carbon dioxide,

CO

2

. You can thus use carbon dioxide's molar mass to convert the mass of carbon dioxide to moles.

Once you know how many moles of gaseous carbon dioxide you have in your balloon, you can use the molar volume of a gas at STP to find the volume occupied by your sample.

Now, more often than not, STP (Standard Temperature and Pressure) conditions are defined as a pressure of

1 atm

and a temperature of

0

∘

C

.

This is actually the old definition of STP conditions, but it's still being taught in schools as being accurate.

The thing to remember about STP conditions is that when the pressure of a gas is set at

1 atm

and the temperature at

0

∘

C

, or

273.15 K

, one mole of that gas occupies

22.4 L

.