[dphuber]

My apologies first off, I'm an ecologist not a chemist.  I'm using acid traps to collect NH3 volatilizing from soils and have had trouble with results.  I likely have a contamination issue but because my numbers all end up approx. equal I want to make sure I'm not saturating the H2SO4 solution.  Below are my calculations but I'm worried I missed something b/c the end value is too low for the method to even work.

Thanks!

2NH3 + H2SO4 --> (NH4)2SO4

Acid trap: 20 mL 2% H2SO4
Stock H2SO4 Ultra grade 98%

C1*V1 = C2*V2   V1 = (.02*.02 L)/.98 = 4.08E-4 L

98% H2SO4 = 17.8 mol/L 

(17.8 mol/L * 4.08E-4 L)/.02 L = 0.3632 mol/L or 2% H2SO4

0.02 L 2%H2SO4 * (0.3632 mol/L)*(2 mol NH3/1 mol H2SO4) = 0.014528 mol NH3

0.014528 mol NH3 * (17 g NH3/mol) = 0.246982 g NH3

0.246982 g NH3 * ( 14 mol N/17 mol NH3) = 0.203397 g NH3-N per 20 mL 2%H2SO4

(0.203397 g NH3-N/20 mL) * (1 L/ 1000 mL) * (1000 mg/1 g) =

0.01016985 mg/L or ppm   
This is 2 orders of magnitude smaller than the analysis is showing.

[Borek]

Please explain further what you are doing, as at the moment I am not sure what you are calculating. 2% w/w sulfuric acid is 0.2M, 20 mL should be enough to capture 8 mmol of ammonia.

[dphuber]

Please explain further what you are doing, as at the moment I am not sure what you are calculating. 2% w/w sulfuric acid is 0.2M, 20 mL should be enough to capture 8 mmol of ammonia.

That is what I'm trying to figure out, how much NH3 I can adsorb with 20 mL of 2% HSSO4.  I need 2% v/v H2SO4 which requires the density of H2SO4 at 98% correct (1.8361 g/mL)?

So I am calculating adsorption correctly just with the wrong Molarity.  The rest of the calculations were to compare theoretical adsorption to what my analysis shows (reported in mg NH3-N/L).  Redoing the calculations using 0.2M I should have a max conc. of 5600 mg/L NH3-N (the original conversion to mg/L is wrong...stupid basic math).