noob question by spudfarm

[jimmy101]

So, for a 20X mix using stoich. propane + air and assuming "20X" means the final pressure in the chamber is 20ATM.

Originally, the air in the chamber was 79.05% N₂ and 20.95% O₂. (Ignoring the trace gases like water, etc.) But, we always add propane until the final percentage is 4.02%, so the N₂ and O₂ have to be decreased by 4.02%. This is the same as mutliplying by (1-0.0402)=0.9598.

So, we calculate the partial pressures of the three main gases;

P_N₂ = (0.7905)(20 ATM)(0.9598) = 15.174 ATM
P_O₂ = (0.2095)(20 ATM)(0.9598) = 4.022 ATM

The amount of propane doesn't get decreased by the 0.9598 factor since 4.02% is the final precentage we are aiming for.
P_propane = (0.0402)(20 ATM) = 0.8040 ATM

Double check that the total pressure comes out to 20 ATM;
P_total = P_N₂ + P_O₂ + P_propane = 15.174 ATM + 4.022 ATM + 0.8040 ATM = 20.00 ATM

Double check that the final propane concentration is indeed the 4.02% we were aiming for;
P_propane/(P_N₂ + P_O₂ + P_propane) = 0.8040 ATM / (15.174 ATM + 4.022 ATM + 0.8040 ATM) = 4.02% propane

Now, the pressure that controls whether or not the porpane liquifies is the propane partial pressure, P_propane, which is only 0.804 ATM. We can look at the graph Spudfarm posted and see that the boiling point at that propane pressure is well below 0°C. So the propane will not liquify in this 20X mixture at normal spudgun temperatures.

[SpudBlaster15]

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras nec placerat erat. Vivamus dapibus egestas nunc, at eleifend neque. Suspendisse potenti. Sed dictum lacus eu nisl pretium vehicula. Ut faucibus hendrerit nisi. Integer ultricies orci eu ultrices malesuada. Fusce id mauris risus. Suspendisse finibus ligula et nisl rutrum efficitur. Vestibulum posuere erat pellentesque ornare venenatis. Integer commodo fermentum tortor in pharetra. Proin scelerisque consectetur posuere. Vestibulum molestie augue ac nibh feugiat scelerisque. Sed aliquet a nunc in mattis.

[DYI]

So I was right

[SpudBlaster15]

Lorem ipsum dolor sit amet, consectetur adipiscing elit. Cras nec placerat erat. Vivamus dapibus egestas nunc, at eleifend neque. Suspendisse potenti. Sed dictum lacus eu nisl pretium vehicula. Ut faucibus hendrerit nisi. Integer ultricies orci eu ultrices malesuada. Fusce id mauris risus. Suspendisse finibus ligula et nisl rutrum efficitur. Vestibulum posuere erat pellentesque ornare venenatis. Integer commodo fermentum tortor in pharetra. Proin scelerisque consectetur posuere. Vestibulum molestie augue ac nibh feugiat scelerisque. Sed aliquet a nunc in mattis.

[DYI]

2) Order KNO3 and KMnO4.
3) Purchase enough brass media to fill my 6" x 9" PVC ball mill jar.

Getting ready for summer already I see