Question

How many moles are in $3.45 \times {10^{24}}\;$ molecules of calcium iodide?

Answer 1

The mole concept is very significant and useful in chemistry. It is actually the base of stoichiometry and it provides the best option to express the amounts of reactants as well as products that are consumed and formed during a chemical reaction.

Complete step by step answer:
To calculate the number of moles, we generally use the following formula:
$Number{\text{ }}of{\text{ }}moles = \dfrac{{Given{\text{ }}mass{\text{ }}}}{{{\text{ M}}olecular{\text{ }}mass{\text{ }}of{\text{ }}the{\text{ }}given{\text{ }}species}}$
We know that 1 mole of any substance contains $6.023 \times {10^{23}}molecules$
Thus, the number of molecules of any substance can be identified by multiplying the number of moles with Avogadro's number i.e. $6.023 \times {10^{23}}$. We can say:
$Number{\text{ }}of{\text{ }}molecules = number{\text{ }}of{\text{ }}moles \times 6.023 \times {10^{23}}$
In the given question, we are provided with the number of molecules of calcium iodide i.e. $3.45 \times {10^{24}}\;$ .
Now substituting this value in the aforementioned formula of number of molecules and rearranging this equation, we can easily get to know the number of moles of calcium iodide as shown below:
$3.45 \times {10^{24}}\; = number{\text{ }}of{\text{ }}moles \times 6.023 \times {10^{23}}$
Rearranging the equation, we will calculate the number of moles as stated below:
$\;number{\text{ }}of{\text{ }}moles = \dfrac{{3.45 \times {{10}^{24}}}}{{6.023 \times {{10}^{23}}}} = 5.728 \simeq 6moles$
Hence, 6 moles are in $3.45 \times {10^{24}}\;$ molecules of calcium iodide.

Note: If we are provided with the given mass of the compound, we can calculate molecular mass of that compound by adding the relative atomic masses of each element present in that particular compound. Then using these two values, we can calculate the number of moles.
Avogadro's number was actually obtained by dividing charge of one mole of electrons by the charge of one single electron that equals $6.02214154 \times {10^{23}}\;$ particles per mole. In order to convert moles into atoms, we can multiply the moles with Avogadro's number and if we want to convert atoms into moles, divide the number of atoms by Avogadro's number.