Question

How would you calculate the number of moles of calcium in 27.0 g Ca?

Answer 1

Hint: Mole is defined as the convenient unit which is used to measure the large number of atoms, molecules or other substance. The mole of the substance is generally equal to \[6.022\times {{10}^{23}}\]elementary entities. It is equal to Avogadro number. These elementary entities can be either the atoms or molecules.

Complete step-by-step answer:So for calculating the number of moles of the substance we need to know the molar mass of that substance. The molar or molecular mass of 1 molecule of substance is defined as the mass which is expressed in the atomic mass unit or the \[\dfrac{1}{12}\] of the mass of one atom of the carbon isotope of carbon-12. The relative molecular mass is the molecular weight of the molecule.
So for calculating the number of moles we need to divide the given mass of the substance by its molar mass. The formula for calculating moles is the following:
\[number of moles=\dfrac{given mass of subs\tan ce}{molar mass of subs\tan ce}\]
The given mass of calcium is 27.0g. while the molar mass of calcium is equal to 40\[gmo{{l}^{-1}}\].
So now substituting the values in formula we get:
\[number of moles=\dfrac{27.0}{40}=0.675\]moles
So the 27.0 g of Ca contains 0.675 moles in it.

Note: If the molecule or the compound was given instead of an element then we have calculated its molecular mass by adding the standard atomic mass of each of the atoms present in the molecules. If the question was asked to calculate the number of atoms in 27.0 g then we would have multiplied the number of moles by the Avogadro number. If the number of molecules was asked then also we would have multiplied the number of moles by Avogadro's number.