Urea, chemical formula #(NH_2)_2CO#, is used for fertilizer and many other things. How do you calculate the number of N,C, O, and H atoms in #1.68 x 10^4# g of urea?

1 Answer
Jul 10, 2017

You have 1680 grams of urea. It means (in it) there are 787 grams of nitrogen, 112 grams of hydrogen, 336 grams of carbon, and 448 grams of oxygen.


Nitrogen = 14 grams
Hydrogen= 1 gram
Carbon = 12 grams
Oxygen= 16 grams

In one mole of urea, we have 28 grams of nitrogen, 4 grams of hydrogen, 12 grams of carbon, and 16 grams of oxygen. In other words, one mole of urea has a molecular weight of 60 grams.

The question is: "If you have 1680 grams of urea, what is the mole number in it?"

The solution of this question: #1680/60 = 28# moles.

Now, what is the elemental weights in 28 moles of urea:

For nitrogen #=28times28=784# grams
For hydrogen #=4times28=112# grams
For carbon #=12times28=336# grams
For oxygen #=16times28=448# grams

The sum of these (#784+112+336+448#) is approximately 1680 grams.