Question

How many moles of pcl3 contain 3.68 × 1025 chlorine atoms?

Answer 1

To answer the question above, we take note first that every mole of PCl₃ contains 3 atoms of Cl. First, we divide the given number by 3.
                                   3.68 x 10²⁵ / 3 = 1.227 x 10²⁵ 
Then, we divide the answer by the Avogadro's number which is equal to 6.022 x 10²³. That is,
                                    1.227 x 10²⁵ / (6.022 x 10²³) = 20.37
Thus, there are 20.37 mol of PCl₃. 

Answer 2

Answer: The moles of $PCl_3$ that contain given number of chlorine atoms is 20.4 moles

Explanation:

We are given:

Number of atoms of chlorine = $3.68\times 10^{25}$

A chemical compound having chemical formula $PCl_3$

In 1 mole of phosphorus trichloride, 1 mole of phosphorus atom and 3 moles of chlorine atoms are present.

According to mole concept:

$6.022\times 10^{23}$ number of molecules occupy 1 mole of a compound.

So, $3\times 6.022\times 10^{23}=1.8066\times 10^{24}$ number of chlorine atoms occupy 1 mole of phosphorus trichloride

Then, $3.68\times 10^{25}$ number of chlorine atoms will occupy = $\frac{1}{1.8066\times 10^{24}}\times 3.68\times 10^{25}=20.4moles$ of phosphorus trichloride

Hence, the moles of $PCl_3$ that contain given number of chlorine atoms is 20.4 moles