Question #164650

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.

(a) Is this reaction exothermic or endothermic? Justify your answer. (5 points)

(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. (10 points)

(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. (10 points)

Expert's answer

(a) Is this reaction exothermic or endothermic? Justify your answer. (5 points)

This reaction is exothermic, as heat energy is released during the process of change. The sign “-“ for ΔH proves this point.

(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. (10 points)

Molar mass of AlCl_{3} is 133.34 g/mol.

310.0 / 133.34 = 2.32 mol

2.32 mol x 705.63 kJ/mol = 1640.5 kJ (released)

Where 705.63 kJ/mol – the enthalpy of formation of AlCl_{3}

(Aluminium chloride (data page) - Wikipedia)

(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. (10 points)

1 mol of AlCl_{3} corresponds to 705.63 kJ (705630 J) of heat transfer

500.0 J / 705630 J = 0.00071 mol

0.00071 mol x 26.98 g/mol = 0.019 g of AlCl_{3}

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