Answer to Question #164857 in General Chemistry for Sarah Khan

Question

Consider the following reaction:

2 Al (s) + 3Cl2 (g) ---> AlCl3 (s) ΔHrxn = -1390.81 kJ/molrxn

(a) Is this reaction exothermic or endothermic? Justify your answer.

(b) Calculate the amount of energy transferred when 310.0 g of AlCl3

forms. Include units and proper sign in your answer. Show all work.

(c) How many grams of Al are required when 500.0 J of energy are

transferred? Include units and proper sign in your answer. Show all work.

Answer 1

a) exothermic, because ∆H=-Q. Q= 1390.81 kJ/mol.

b) 310 x 1390.81 / 133.5 = 3 229,59625.

c) 0.5 x 54/1390.81 = 0,0194131477 g.