Stoichiometry: 2Al +3ZnCl(2) 2AlCl(3) +3Zn. How many grams of Zn can be produced by treating 81g al with zinc chloride? I need to find the answer using Unit Analysis.

Question

Stoichiometry: 2Al +3ZnCl(2) <=> 2AlCl(3) +3Zn. How many grams of Zn can be produced by treating 81g al with zinc chloride? I need to find the answer using Unit Analysis.

espex · Answer

Well this is going to be a pain to type and worse with their drawing util. Basically what you need to do is realize that your balanced equation tells you how many moles of each compound are needed for this reaction. You are given grams, so need to figure out how many moles you need to equal 81g of al, just under 3moles. Your unit analysis is going to involve you converting the number of moles to grams and then working through the equation.

espex · Answer

You have 81g @ 1mol/26.98g = 3.0mol Using a simple ration, your equation puts you with 2mols Al : 3mols Zn. So 2/3 as 3/x. 2x=9, x=9/2 which is 4.5moles of Zn @ 65.41g/mol = 294.345g Making sure to round to the proper number of sigfigs.