Ammonium dihydrogen phosphate, formed from the reaction of phosphoric acid with ammonia, is used as a crop fertilizer as well as a component of some fire extinguishers, (a) what are the mass percentages of n and p in the compound? (b) how much ammonia is incorporated into 100. g of compound?

a)The mass percentages of nitrogen and phosphorus in the compound is 24.34% and 26.95% respectively.

b) 14.78 grams ammonia is incorporated into 100. g of compound.

Explanation:

a) Ammonium dihydrogen phosphate that is .

Molecular mass of ammonium dihydrogen phosphate = M

M = 115 g/mol

Percentage of an element in a compound:

Percentage of nitrogen:

Percentage of phosphorus:

b) Percentage of ammonia in 1 molecule of ammonium dihydrogen phosphate.

Molar mass of ammonia = 17 g/mol

Amount of ammonia in 100 grams of compound:

14.78% of 100 g of ammonium dihydrogen phosphate:

14.78 grams ammonia is incorporated into 100. g of compound.

n2(g) + 3h2-> 2nh3(g)   this is the balanced equation

note the mole ratio between n2, h2 and nh3.   it is 1 : 3 : 2   this will be important.

moles n2 present = 28.0 g n2 x 1 mole n2/28 g = 1 mole n2 present

moles h2 present = 25.0 g h2 x 1 mole h2/2 g = 12.5 moles h2 present

based on mole ratio, n2 is limiting in this situation because there is more than enough h2 but not enough n2.

moles nh3 that can be produced = 1 mole n2 x 2 moles nh3/mole n2 = 2 moles nh3 can be produced

grams of nh3 that can be produced = 2 moles nh3 x 17 g/mole = 34 grams of nh3 can be produced

note:   the key to this problem is recognizing that n2 is limiting, and therefore limits how much nh3 can be produced.