Question

If the sum of the total number of protons and neutrons in in a pure sample of $MgC{l}_2$ is $1.132\times {10}^{26}$ then calculate the total number of moles of chlorine atoms present in the sample.
(consider all $Cl$ atoms to be $Cl-35$)

• A. 4 mol
• B. 2 mol
• C. 3 mol
• D. 5 mol

Answer 1

The correct option is A 4 mol

The sum of protons and neutrons in Mg $=12+12=24$

The sum of protons and neutrons in Cl $=17+18=35$

The total sum of protons and neutrons in one molecule of $MgC{l}_2=24+35\times 2=94$

The total sum of protons and neutrons in one mole of $MgC{l}_2=94\times 6.022\times {10}^{23}$

$92\times 6.022\times {10}^{23}$ protons and neutrons are present in 1 mole of $MgC{l}_2$.

So, $1.132\times {10}^{26}$ protons and neutrons will be present in
$=\frac{1.132\times {10}^{26}}{94\times 6.022\times {10}^{23}}$ mole of $MgC{l}_2$
= 2 moles of $MgC{l}_2$

Again 1 mole of $MgC{l}_2$ contains 2 moles of $Cl$ atoms.

So, 2 moles of $MgC{l}_2$ will contain 4 moles of $Cl$ atoms.