Im not sure where to factor in the two longer compounds for this problem.

"Rank the given compounds based ontheir relative acidities"

HF
H2C--CH2
NH3
CH4
HC---CCH3

This is the order i thought it was, but this isnt right apparently...

(--- means triple bond, -- means double bond)

3 answers

You didn't post the order you thought was correct. And the problem doesn't say increasing acidity or decreasing acidity.
From least acid to most acid.
NH3
CH4
ethylene
methyl acetylene
HF
H atoms on double and triple bonded carbon are acidic, triple bonds always moreso than double bonded C.
okay thanks but that was wrong actually
Sorry about that. I mixed up the NH3 and CH4
As a series, they go across the periodic table like this.
CH4 NH3 H2O HF with HF being the most acid and CH4 the least acid. Actually, I typed it that way the first time but the computer didn't post it and when I redid it I screwed up.