Answer to Question #279149 in General Chemistry for kate

Question

1.      When 1.42 g of iron reacts with 1.8 g of chlorine, 3.22 g of  and 8.6 kJ of heat is produced.  What is the enthalpy change in kJ for the reaction when 1 mole of  is produced?  

                                      

Answer 1

Step 1: Data given

Mass of iron = 1.42 grams

Mass of chlorine = 1.80 grams

Mass of FeCl2 = 3.22 grams

Heat produced = 8.60 kJ (ΔH = -8.60 kJ because the reaction is exothermic)

Molar mass of Fe = 55.845 g/mol

Molar mass of Cl2 = 70.9 g/mol

Molar mass of FeCl2 = 126.75 g/mol

Step 2: The balanced equation

Fe + Cl2 → FeCl2

Step 3: Calculate moles of FeCl2

Moles FeCl2 = Mass FeCl2 / Molar mass FeCL2

Moles FeCl2 = 3.22 grams / 126.75 g/mol

Moles FeCl2 = 0.0254 moles

Step 4: Calculate the enthalpy change for 1 mole of FeCl2

For 0.0254 moles of FeCl2 ΔH is -8.60 kJ

For 1 mole of FeCL2 ΔH = -8.60 / 0.0254mol = -338.58 kJ/mol

ΔH for 1 mole of FeCl2 is -338.58 kJ/mol