Question

How many atoms of Cl are there in 35.5 into 10 raised to minus 5 gram of chlorine..?

Answer 1

This question is testing the concept of Avogadros constant.

Avogadros constant is :

1 mole = 6.022 × 10²³ atoms

The moles of Cl are :

Moles = mass / molar mass

Mass = 0.00001 grams

Molar mass = 35.5

Moles = 0.00001/35.5 = 2.82 × 10⁻⁷ moles

Molecules = 2.82 × 10⁻⁷ × 6.022 × 10²³

= 1.696 × 10¹⁷ atoms.

Answer 2

Given mass of chlorine is 35.5$10^{-5}$ grams.

Molar mass of chlorine is  35.45 g/mol.

Converting mass of chlorine to moles using the molar  mass:

$35.5*10^{-5} * [tex]\frac{1mol}{35.45 grams}$

= $1*10^{-5}$ moles.

Converting moles of chlorine to atoms using the conversion factor one mole =$6.023*10^{23}$ atoms:

= $1*10^{-5}$ moles$\frac{1mol}{6.022*10^{23} }$

=$1.6*10^{-29}$ atoms.