Question

How many atoms of lithium are there in $3.45$ moles?

Answer 1

To solve this type of questions firstly we need to calculate number of moles lithium of at present then we have to multiply the given number of moles by Avogadro's number for finally find out the actual numbers of moles and mole concept The mole is unit of measurement for a amount of the substance in system. A mole of the substance is the mole of particle which are defined as containing exactly by Avogadro's number $6.022\times {{10}^{23}}$

Complete solution:
We know that the inter relationship between atoms and moles is given by
$1moleAtoms=6.022\times {{10}^{23}}atoms$
Also the mole concept can be defined as the convenient method of which we had to express using an amount of materials as well as any measurement could be broken down to two parts and numerical magnitude and units that magnitude is expressed itself.
So in order to determine that how many atom are being occupy by a given number of moles and then to multiply provided moles by $6.022\times {{10}^{23}}atoms$
In such cases we have around of $3.45$ moles lithium $Li$
$3.45molLi\times \frac{6.022\times {{10}^{23}}Atoms Li}{1mol Li}=2.08\times {{10}^{24}}Atoms Li$

Therefore $2.08\times {{10}^{24}}atoms$ of lithium are in $3.45$ moles.

Note: Note that the mole concept simplifies mass relation among reactant and product like we can have base and our calculation on coefficient number of molecules involved in reaction.
Also before solving we should know the atom concept and atomic theory which includes molecular weight and mass and the formula required for the atoms. At the same time mass of substances are on a lab scale unit.