Question

How many moles are there in ${\text{400}}{\text{.0}}$ grams of carbon?

Answer 1

In the above question we are asked to find out the number of moles present in g of carbon. We know that the atomic mass of an element or molar mass of a compound contains 1 mole. So, basically here we have to find the atomic mass of carbon and we have to compare it with the number of moles.
Formula used: ${\text{moles}} = \dfrac{{{\text{mass}}}}{{{\text{molar mass}}}}$

Complete step by step solution:
We know 1 mole of an element contains atomic mass of that element.
As atomic mass of carbon = 12.
So, 12g of carbon contains 1 mole of carbon.
Hence, ${\text{400}}{\text{.0}}$ g of carbon contains $\dfrac{{{\text{400}}}}{{{\text{12}}}}{\text{ = 33}}{\text{.33}}$ moles of carbon.
Therefore, ${\text{33}}{\text{.33}}$ moles of carbon are present in ${\text{400}}{\text{.0}}$ g of carbon.

Additional information:
One mole of a compound contains Avogadro’s Number of particles. Avogadro’s number is used in chemistry to deal with large numbers. It is the basis of the mole unit of measurement. It is a simple way of conversion between mole, mass and number of molecules. Suppose, to get the number of particles present in a substance, first, we have to find the number of moles present in it and then by using Avogadro’s number we can find the number of particles present inside it.

Note:
Avogadro’s number is kind of generalized number, hence, we can write:
1 mole = $6.022 \times {10^{23}}$ atoms, or molecules, or protons, or electrons etc.
In short, it is the number of particles in a mole.
1 mole of an element contains atomic mass of the element.
Hence, in order to solve these types of questions, we have to first decide which quantity (electron, proton, atom) is equivalent to Avogadro’s number.
At STP, one mole of any gas occupies a volume of ${\text{22}}{\text{.4}}$ L.