Question

How many moles of silver nitrate do $2.888\times {{10}^{15}}$ formula units equal?

Answer 1

Hint:‌Before talking about the answer, you should know the basic formula to calculate the number of moles, which is equal to weight per molar mass of the compound. So, to calculate the mass of the compound, you will need to multiply weight with the number of moles.


Complete answer:
Moles is defined as a scientific unit which is used to measure large quantities of atoms and molecules. It is defined as the amount of substance present in a sample.
Avogadro’s number is defined as the proportionality factor that tells the relationship between the number of constituent particles with the amount of substance in a sample. Its SI unit is $mo{{l}^{-1}}$ . It is denoted with a symbol, ${{N}_{A}}$ .
${{N}_{A}}=6.023\times {{10}^{23}}mo{{l}^{-1}}$
Here, it is given that the number of molecules of silver nitrate is $2.888\times {{10}^{15}}$
The Avogadro’s number is equal to $6.023\times {{10}^{23}}mo{{l}^{-1}}$
To calculate the number of moles, we can use the formula:
$M=n\times {{N}_{A}}$
where, $M$ is the number of molecules, $n$ is the number of moles and ${{N}_{A}}$ is the Avogadro’s number.
$n=\dfrac{M}{{{N}_{A}}}$
Now, substituting the values of Avogadro’s number and number of molecules in the above formula, we get,
$n=\dfrac{2.888\times {{10}^{15}}}{6.022\times {{10}^{23}}}$
$n=0.47\times {{10}^{-8}}$ or $4.7\times {{10}^{-9}}\,mol$

Therefore, the number of moles of silver nitrate in $2.888\times {{10}^{15}}$ formula units is equal to $4.7\times {{10}^{-9}}\,mol$.


Note:Sometimes, We often get confused between moles and molecules, that is why we should know the meaning of both of them. Mole is used to measure the quantity of the substance and has the same number of atoms present, whereas a molecule is defined as a species that is formed by the combination of several atoms through chemical bonding. One mole is said to be the number of particles present in $12\,g$ of $C-12$ isotope.