Question

The mass of nitrogen in 1 Kg of ammonium nitrate is:
A.700 g
B.3.5 x 10-1 Kg
C.350 g
D.35 g

Answer 1

Hint: Nitrogen is the most abundant element found in the earth crust and is the element number 7 of the periodic table it has electronic configuration of 2, 5 and is the non- metal in nature .The nitrogen atom has a lone pair of electron in its structure of ammonia molecule.

Complete answer: The ammonium nitrate is basic in nature and it has the molecular formula:$N{H_4}N{O_3}$and its molecular weight is 80 grams.
Thus in the 80 grams of ammonium nitrate as it is evident from the formula 2 nitrogen atoms are present , thus the molecular mass of the nitrogen atoms will be:
2x molecular weight of one nitrogen atom
=2 x 14= 28 grams.
We know that 1 Kg=1000 gram
Thus, the mass of nitrogen in 1 Kg or 1000 gram of ammonium nitrate will be:
$ = \dfrac{{28 \times 1000}} {80}$
 = 350grams
The molar mass of the compound is the amount of the mass of the sample of that compound divided by the amount of the substance in that sample. Usually the amount is calculated in moles, thus molar mass is a bulk property and not the molecular property. The average is usually taken due to the presence of the isotopes in the sample.

Thus the option C. 350 g is the correct answer..

Note:
The molar mass is the intensive property and it depends on the size of the sample. The SI unit of molar mass is kg/mol. However g/ mol is commonly used for calculations. The units in the SI and CGS systems are interconvertible so they can be easily converted from one form to another.