What is the percentage of ammonia in the sample?

  • Thread starter Thread starter tag16
  • Start date Start date
  • Tags Tags
    Ammonia
AI Thread Summary
The discussion revolves around calculating the percentage of ammonia in a sample based on the formation of platinum from ammoniacal nitrogen. A participant attempted to calculate the percentage using the mass of platinum produced but arrived at 41.5%, which contradicts the book's answer of 38.74%. Confusion arises regarding the correct use of ammonia (NH3) versus ammonium (NH4) in the calculations. The calculations performed were critiqued for possibly using incorrect units and stoichiometric factors. Ultimately, the consensus is that the book's answer is correct, suggesting a need for clarity in the calculations involving ammonia and its molecular mass.
tag16
Messages
95
Reaction score
0

Homework Statement



Ammoniacal nitrogen can be determined by treatment of the sample with chloroplatinic acid; the product is slightly soluble ammonium chloroplatinate: H2PtCl6 + 2NH4 --> (NH4)2PtCl6 + 2H

The precipitate decomposes on ignition, yielding metallic platinum and gaseous products:
(NH4)2PtCl6 --> Pt(s) + 2Cl2(g) + 2NH3(g) + 2HCl(g)

Calculate the percentage of ammonia in a sample if 0.2115g gave rise to 0.4693g of platinum.

Homework Equations





The Attempt at a Solution



0.4693(1/(14+1+1+1))= 0.0276
0.0276(2)(159)= 8.778
8.778/0.2115= 41.5%

did I do this right? The back of my chemistry book says that the answer should be 38.74% NH3, so if this is correct how would you arrive at this answer?
 
Physics news on Phys.org
Did you use NH4 or NH3 as ammonia is NH3. Might be a mistake there as for Molecular mass 17 the result is the one in the book.
 
tag16 said:
0.4693(1/(14+1+1+1))= 0.0276
0.0276(2)(159)= 8.778
8.778/0.2115= 41.5%

Please elaborate, I have no idea what you did. You started dividing mass of platinum by the molar mass of ammonia, next you multiplied the result by 2 (stoichiometric coeffcient) and by molar mass of platinum (with digits reversed to make it harder to guess what you did). From what I understand at this stage your result is in rather unexpected units:

\frac {(g_{Pt})^2 (mol_{NH_3})^2} {g_{NH_3} (mol_{Pt})^2}

I doubt that's what you wanted to do, from the last operation seems like you think at this stage you have mass of ammonia multiplied by 100.

Book answer is correct.
 
Last edited by a moderator:
Lok said:
Did you use NH4 or NH3 as ammonia is NH3. Might be a mistake there as for Molecular mass 17 the result is the one in the book.

Btw. With 18 I get the same wrong result as you. The things you wrote here make sense but weird that you don't get the result.
 
I don't get how to argue it. i can prove: evolution is the ability to adapt, whether it's progression or regression from some point of view, so if evolution is not constant then animal generations couldn`t stay alive for a big amount of time because when climate is changing this generations die. but they dont. so evolution is constant. but its not an argument, right? how to fing arguments when i only prove it.. analytically, i guess it called that (this is indirectly related to biology, im...
Back
Top