Hello, A H.,
2AI (s)+ 3Cl2 ---> AICl3
The equation isn't balanced: There needs to be one more aluminum chloride to account for the 2 Al and 6 Cl coming in.
2AI (s)+ 3Cl2 ---> 2AICl3
Convert the Al and Cl2 masses into moles of each:
Al : 0.556 moles
Cl2 : 0.212 moles
The molar ratio of Cl2 to Al is 1.5 Cl2 per 3 Al. We can see that there won't be nearly enough Cl2 to react with all of the aluminum. Cl2 is the limiting reagent. We can assume all of it reacts, so use the entire 0.212 moles of Cl2 to determine how much Al is consumed.
The molar ratio of Al to Cl2 is (2 moles Al/3 moles Cl2), or 2/3.
Determine the moles Al consumed:
(0.212 moles Cl2)*(2 moles Al/3 moles Cl2) = 0.141 moles Al consumed
That would leave 0.414 moles of Al unreacted. That is 11.192 grams.
The molar ratio of the product to the Al is 2 moles AlCl3 per 2 moles Al, or 1 to 1.
That means we formed 0.141 moles of AlCl3
Convert the moles AlCl3 produced to grams: (0.141 moles AlCl3)*(133.35 g/mole) = 18.81 grams AlCl3.
We should be able to account for ther full 15 grams of reactants, regardless of how they are ti4ed up in molecules.
18.81 grams AlCl3 produced
18.81 grams AlCl3 produced
11.192 grams Al left behind
30,0 grams total
It's all accounted for.
Bob