Question

Show your work for all calculations.

1. When 1.104 grams of iron metal are mixed with 26.023 grams of hydrochloric acid in a coffee cup calorimeter, the temperature rises from 25.2 °C to a maximum of 33.5 °C. The reaction that occurs is given below.

2Fe(s)+6HCl(aq) → 2FeCl3 (aq)+3H2 (g)

a) Determine the amount of heat (in J) absorbed by the reaction mixture. Assume that the specific heat capacity of the mixture is the same as the specific heat capacity of water.

b) How much heat (in J) was released by the reaction that occurred?

c) Is this reaction exothermic or endothermic? Is ΔHreaction positive or negative?

d) Under constant pressure conditions (as used in this experiment), the heat released by the reaction equals the reaction enthalpy, qreleased = ΔHreaction. Determine ΔHreaction in Joules per gram of metal used (J/g).

e) Determine ΔHreaction in kilojoules per mole of metal used (kJ/mol).

f) Determine ΔHreaction in kilojoules per mole for the balanced reaction equation provided (kJ/mol). 

2. Consider the following three reactions:

2Fe(s)+6HCl(aq) → 2FeCl3 (aq)+3H2 (g) ΔHA

Fe2O3 (s)+6HCl(aq) → 2FeCl3 (aq)+3H2O(l) ΔHB

2H2 (g) + O2 (g) → 2H2O(l) ΔHC

Show how these equations must be summed together according to Hess’s Law to determine ΔH for the combustion of iron (target equation shown below). Also show clearly how the ΔH values of each of the three reactions must be manipulated to determine the enthalpy of combustion of iron.

4Fe(s)+3O2 (g) → 2Fe2O3 (s) ΔH=?

3. Using tabulated ΔHf° values in the text, determine the enthalpy change (in kJ/mol) that occurs during the formation of water from its elements as described by the equation:

2H2 (g) + O2 (g) → 2H2O(l) ΔH=?