How many atoms are in each elemental sample?

(a) 16.9 gSr

(b) 26.1 gFe

(c) 8.55 gBi

(d) 38.2 gP

Solution 37P

Here, we are going to calculate the number of atoms in each of the given elemental sample.

Step 1:

One mole of any species is that quantity in number having a mass equal to its atomic or molecular mass in grams.

The number of particles (atoms, molecules or ions) present in 1 mole of any substance is fixed, with a value of 6.022 × 1023. This is an experimentally obtained value. This number is called the Avogadro Constant or Avogadro Number.

Step 2:

Therefore, 1 mole = molar mass

1 mole = Avogadro number of particles

Combining the two statements, we get,

Molar mass = Avogadro's number of particles

Therefore, number of particles in a given mass = (Avogadro's number / molar mass) x given mass

Thus,

The number of atoms in a given elemental sample = (given mass/molar mass) x Avogadro number