Ammonia sulfate (NH2)2SO4 is used in fertilizer. What is the mass percent compostionof (NH4)2SO4?

Question

I don't khow what I'm doing wrong 

 

Answer 1

They're asking you to find the percent of each element in (NH₄)₂SO₄.  So you need to find the atomic mass of each element's contribution and divide by the total.  To do this, you'll need to consult a periodic table, or some other chart that lists the atomic masses.

 

First you have to interpret the formula.  (NH₄)₂SO₄ means that there are 2 NH₄'s and 1 SO₄.  That means 2 N's, 8 H's, 1 S and 4 O's.  So work it our as follows:

 

N: atomic mass = 14.007.  2 N's = 28.014

H: atomic mass = 1.008.  8 H's = 8.064

S: atomic mass = 32.06.  1 S = 32.060

O: atomic mass = 15.999.  4 O's = 63.996

 

Now add them up to find the total.  That's 132.134.

 

Now use a calculator to divide each element's contribution by the total to get the percent for each:

 

N:  28.014 / 132.134 = .2120 = 21.20 %

H:  8.064 / 132.134 = .0610 = 6.10 %

S:  32.060 / 132.134 = .2426 = 24.25 %

O:  63.996 / 132.134 = .4843 = 48.43 %

 

The percentages should add to 100, but they don't quite, because of rounding "error," which is common during calculations like this.