How many molecules are in 3.40 mol He?

20.5 * 10²³ molecules of He

Explanation:

Given dа ta:

Number of moles of He = 3.40 mol

Number of molecules of He = ?

Solution:

The given problem will solve by using 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.

The number 6.022 * 10²³ is called Avogadro number.

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

For 3.40 moles of He:

3.40 mol * 6.022 * 10²³ molecules

20.5 * 10²³ molecules of He