I'm doing a final lab for my Chemistry class, which entails the reaction of Aluminium and hydrochloric acid to produce gas that we are supposed to collect in mL. I have been assigned to collect exactly 215 mL = .215 L but I must have the correct amount of Aluminium to produce the amount of gas. What formula template would I have to use to determine the amount of Al needed to produce .215 mL of gas?

Question

I'm doing a final lab for my Chemistry class, which entails the reaction of Aluminium and hydrochloric acid to produce gas that we are supposed to collect in mL. I have been assigned to collect exactly 215 mL = .215 L but I must have the correct amount of Aluminium to produce the amount of gas. What formula template would I have to use to determine the amount of Al needed to produce .215 mL of gas?

Answer 1

I don't know how your are to collect the H2 gas. I will assume you will use displacement of air and not displacement of water. Also, what is the temperature and barometric pressure when you do the experiment.

2Al + 6HCl --> 2AlCl3 + 3H2
Use PV nRT to solve for n = mols at T and P of the room.
Then convert mols H2 gas to mols Al needed by
mols Al = mols H2 x (2 mols Al/3 mols H2) = ?
Finally, convert mols Al to grams. g = mols x atomic mass Al = ?

You may use displacement of water to collect the H2 gas. If so you must correct for the vapor pressure of water at the T of the room at the time of the experiment.
Ptotal = pH2 + pH2O
Ptotal = barometric pressure in the room.
pH2O is available from a table supplied by the prof or in the back of your lab manual/text/internet. Solve for pH2 from that calculate n = mols H2 from the PV = nRT from above. Post your work if you get stuck. Good luck.