Question

How many atoms are in 39.2 g of calcium?

a) 6.022 x 10^23 aoms
b) 235.2 x 10^23 atoms
c) 5.89 x 10^23 atoms
d) 40.08 x 10^23 atoms

Answer 1

5.89× 10²³ atoms of Ca

Step-by-step explanation:

Given data:

Mass of Ca = 39.2 g

Number of atoms = ?

Solution:

Number of moles of Ca:

Number of moles = mass/molar mass

Number of moles = 39.2 g/40.078 g/mol

Number of moles = 0.978 mol

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.

1 mole = 6.022 × 10²³ atoms

0.978 mol × 6.022 × 10²³ atoms / 1 mol

5.89× 10²³ atoms of Ca