Suppose "Element X" has a molar mass of 38.5 g/mol. How many atoms of Element X would be present in 2.78 mol?

16.74×10²³ atoms

Explanation:

Given data:

Number of moles of X = 2.78 mol

Number of atoms = ?

Solution:

According to Avogadro number.

1 mole of any substance contain 6.022×10²³ atoms. Thus,

2.78 mol × 6.022×10²³ atoms / 1 mol

16.74×10²³ atoms

The number 6.022 × 10²³ is called Avogadro number.

It is the number of atoms , ions and molecules in one gram atom of element, one gram molecules of compound and one gram ions of a substance.

For example,

18 g of water = 1 mole = 6.022 × 10²³ molecules of water

1.008 g of hydrogen = 1 mole = 6.022 × 10²³ atoms of hydrogen

particle   p is an electron and particle q is a neutron