Question

How many moles are in \[9.8\] grams of calcium?

Answer 1

Hint: We have to know that the number of atoms, molecules, monatomic ions and polyatomic ions and all other particles like electrons are represented in terms of moles. Hence, we can say that the mole is a chemical unit. Consider an example, the mass of one mole of carbon exactly equal to \[12g\] and it contains Avogadro number of carbon atoms which is equal to \[6.0223 \times {10^{23}}\] and this Avogadro number is expressed by \[{N_A}\].

Complete answer:
As we know that calcium is a chemical element having the symbol $'Ca'$ with atomic number \[20\]. The chemical properties and physical properties of calcium are the same as its heavier homologous barium and strontium. The oxidation number of calcium is equal to \[ + 2\].
To find out the number of moles that are in \[9.8\] grams of calcium, first we have to find out the amount of grams that are in one mole of calcium.
The mass of one mole of calcium is equal to \[40.08g\]. Hence, to calculate the number of moles present in \[9.8g\] of calcium, we have to divide the given mass of the sample with the mass of one mole.
Number of moles \[ = \dfrac{{\text{mass of sample}}}{{\text{mass of 1mole}}}\]
Substitute the values in the above equation,
\[\dfrac{{9.8g}}{{40.08g}} = 0.2445moles\]
Therefore, the number of moles in \[9.8\] grams of calcium is equal to \[0.2445\] moles.

Note:
We need to know that the number of moles can be found by dividing the given mass of the sample with the mass of one mole. And calcium is the most abundant metal present in the earth. In the human body, it is the fifth most abundant element. And calcium is an alkaline earth metal and it is a more reactive metal. When it is exposed to the air, there is a formation of a dark oxide nitride layer.