Answer:
3.1x10²³
Explanation:
I'm going to answer the question assuming the number of molecules of FeCl₃ is asked, rather than the number of atoms.
First we convert 9.3x10²³ atoms of HCl into moles of HCl, using Avogadro's number:
Then we convert 1.54 moles of HCl into moles of FeCl₃, using the stoichiometric coefficients of the reaction:
Finally we calculate how many FeCl₃ molecules are there in 0.51 moles:
The closest option is 3.1x10²³.
The number of atoms produced is four times the number of FeCl₃ molecules produced.