Question

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).

Answer 1

Answer:

a) An exothermic reaction, will release heat. No heat will be absorbed.

b) 903.71 J  of heat released

c) reaction is exothermic and ∆H will be negative.

d) ΔHreaction = 818.6 J/g

e)  ΔHreaction = 45.6 kJ/mol

f) ΔHreaction = 91.2 kJ

Explanation:

Step 1: Data given

Mass of iron = 1.104 grams

Mass of hydrochloric acid = 26.023 grams

Initial temperature = 25.2°C

Final temperature = 33.5 °C

Temperature change = 8.3 °C

Step 2: The balanced equation

2Fe(s)+6HCl(aq) → 2FeCl3 (aq)+3H2 (g)

(A)  Determine the amount of heat (in J) absorbed by the reaction mixture.

Since we have a rise of temperature, this means the reaction is exothermic.

An exothermic reaction, will release heat. No heat will be absorbed.

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

q = mC∆T

with q = heat released (in J)

with m = the mass (in grams)

with c = the specific heat capacity (in J/g°C)

with  ∆T  = The change in temperature (in °C)

q = (26.023g)*(4.184 J/g°C)*(8.3 °C) = 903.71 J  of heat released

(C)  Is this reaction exothermic or endothermic? Is ΔHreaction positive or negative?

Since we have a rise of temperature, this means the reaction is exothermic.

There is heat released so ∆H will be 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).

ΔHreaction = 903.71 J/1.104 g = 818.6 J/g

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

Number of moles of iron =1.104 grams / 55.845 g/mol = 0.0198 moles

ΔHreaction = 903.71 J / 0.0198 moles = 45641.9 J/mol = 45.6 kJ/mol

(F)  Determine ΔHreaction in kilojoules per mole for the balanced reaction equation provided

Since we have 2moles of Fe in the balanced reaction;

ΔHreaction = 45.6 kJ/mol * 2 mol = 91.2 kJ