Question

How many moles are in 225 grams is NaCl

Answer 1

Explanation:

Stoichiometry is the quantitative study of the mass relation of reactants and products in a chemical reaction to determine the amount of reactant required for a reaction to produce a specified quantity or to determine the theoretical yield for the products.

The mole is an SI base unit to measure the amount of elementary entities (atom, molecules, ions, electrons, particles, etc.) of a given mass of a particular substance. One mole is the quantity of a substance exactly equal to Avogadro's number which is approximately 6.022 $\times \ 10^{23} \ \ \text{mol}^{-1}$.  

For a stoichiometric calculation for gram-to-mole conversion, the conversion follows the relation

                                                       $n \ = \ \displaystyle\frac{m}{M_{r}}$,

where $n$ is the number of moles of a given substance, $m$ is the mass of the substance and $M_{r}$ is the molecular weight of the substance.

Given that the substance of interest is sodium chloride, NaCl, the molecular weight of the compound is

                                           $M_{r} \ = \ A_{r}(\text{Na}) \ + \ A_{r}(\text{Cl}) \\ \\ M_{r} \ = \ 23 \ + \ 35.45 \\ \\ M_{r} \ = \ 58.45 \ \text{g mol}^{-1}$,

where $A_{r}$ is the atomic mass of the element.

Therefore, the number of moles of sodium chloride is

                                            $n \ = \ \displaystyle\frac{255 \ \text{g}}{58.45 \ \text{g mol}^{-1}} \\ \\ n \ = \ 4.363 \ \text{mol} \ \ \ \ \ \ \ \ (\text{4 \ s.f.})$