Question

Worldwide, scientists are working on different options for clean energy to replace the burning of fossil fuels. One option that could potentially be successful is the use of hydrogen gas. This gas carn be generated through a reaction between carbon and water. C(s) + 2H2O(g) → CO2(g) + 2H2(g) ΔH= ? CO2(g) → C(s) +O2(g) ΔH 393.5 KJ 2H2O(g) → 2H2(g) + O2(g) ΔH = 483.6 KJ Use the chemical equation and Hess's law to determine the heat of formation and if this reaction is exothermic or endothermic.

Answer 1

The heat of formation is 90.1 KJ and the reaction is endothermic.

Step-by-step explanation:

Chemical equations can be treated as algebraic equations and their enthalpy of reaction can be added or subtracted according to the operation applied. In the given problem, we have to determine the heat of formation of hydrogen gas using the given two equations. which are

CO₂(g) → C(s) +O₂(g) ΔH₁ = 393.5 KJ --------------------------------------- (1)

2H₂O(g) → 2H₂(g) + O₂(g) ΔH₂ = 483.6 KJ --------------------------------------- (2)

It can be seen from the above equation that by inversing the first equation (its enthalpy of reaction becomes negative) and adding equation 2 with it we obtain the desired equation, this is shown below

C(s) + O₂(g) → CO₂(g) ΔH₃ = -393.5 KJ ------------------------------------ (3)

2H₂O(g) → 2H₂(g) + O₂(g) ΔH₂ = 483.6 KJ --------------------------------------(2)

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C(s) + 2H₂O(g) → CO₂(g) + 2H₂(g)

The heat of formation of this equation can be calculated from equation 3 and 2, mathematically expressed as,

ΔH = ΔH₃ + ΔH₂

ΔH = -393.5 KJ + 483.6 KJ

ΔH = 90.1 KJ

The heat of formation is positive, hence the reaction is endothermic.

Answer 2

DH = +90kJ

The reaction is endothermic.

Step-by-step explanation:

Hess law states that regardless of the multiple steps a reaction takes, the total enthalpy of the reaction is the sum of all the multiple steps taken.

C(s) + 2H2O(g) → CO2(g) + 2H2(g) ΔH= ?

CO2(g) → C(s) +O2(g) ΔH = -393.5 KJ 2H2O(g) → 2H2(g) + O2(g) ΔH = -483.6 KJ

DH = DHproduct- DHreactant

= -393.5kJ -(-483.6kJ)

= 90.1kJ

Overall reaction equation:

C(s) + O2(g) + 2H2O(g) --> CO2(g) + 2H2(g) + O2(g)

The reaction is endothermic because the value of the total enthalpy is positive therefore no heat is lost to the surroundings.

Attached below is the hess law chart drawn for better understanding.