Question

Be sure to answer all parts. Calculate the number of Natoms in 2.75 mg of NH NO3. x 10 Natoms Enter your answer in scientific notation.

Answer 1

GIVEN DATA:

Mass = 2.75 mg

Molecular formula of the compound = NH4NO3

Molecular mass = 80.043g/mol

converting mass into grams:

1000 mg = 1 g

2.75 mg = ? g

2.75 mg X 1 / 1000 = 2.75 X 10-3  g

finding the number of moles:

n = (mass of NH4NO3 ) / (molar mass of NH4NO3)

n = 2.75 X 10-3 g / 80.043 g/mol

   = 3.45 x 10-5 mol.

Calculate the number of atoms of NH4NO3:

Number of atoms of NH4NO3 = number of mol. X Avogadro’s number

   = 3.45 X 10-5 mol. X 6.023 X 1023

= 2.07 x 1019 atoms

Calculating number of N atoms,

There are 9 atoms in NH4NO3 in which 2 atoms are nitrogen.

If 9 atoms consits of 2.07 x 1019 atoms.

Then 2 atoms of nitrogen has ,

= (2 x 2.07 x 1019 ) / 9

=4.6 x 1018 atoms.

Therefore there are 4.6 x 1018 atoms of N in 2.75 mg of NH4NO3.