Respuesta :
When the enthalpy of this overall chemical equation is calculated, the enthalpy of the second intermediate equation is halved and has its sign changed.
Let's consider the following intermediate chemical reactions.
Reaction 1: Ca(s) + CO₂(g) + ½O₂(g) → CaCO₃(s) ΔH₁ = -812.8 kJ
Reaction 2: 2 Ca(s) + O₂(g) → 2 CaO(s) ΔH₂ = -1269 kJ
We want to calculate the enthalpy of the following overall chemical equation.
CaO(s) + CO₂(g) → CaCO₃(s) ΔH = ?
We can apply Hess' law.
What is Hess' law?
Hess' law states that regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of all changes.
To apply Hess' law in this case we have to:
- Conserve equation 1 as is.
- Reverse equation 2 and multiply it by 1/2, thus changing the sign of its enthalpy and multiplying it by 1/2.
- Add both equations and their enthalpies.
Ca(s) + CO₂(g) + ½ O₂(g) → CaCO₃(s) ΔH = -812.8 kJ
+
CaO(s) → Ca(s) + ½ O₂(g) ΔH = 634.5 kJ
--------------------------------------------------------------------------------------
CaO(s) + CO₂(g) → CaCO₃(s) ΔH = -178.3 kJ
When the enthalpy of this overall chemical equation is calculated, the enthalpy of the second intermediate equation is halved and has its sign changed.
The complete question is as follows.
Consider the intermediate chemical reactions.
Ca (s) + CO₂ (g) + ½O₂ (g) → CaCO₃ (s) ΔH₁ = -812.8 kJ
2Ca (s) + O₂ (g) → 2CaO (s) ΔH₂ = -1269 kJ
The final overall chemical equation is
CaO (s) + CO₂ (g) → CaCO₃ (s) ΔH = ?
When the enthalpy of this overall chemical equation is calculated, the enthalpy of the second intermediate equation
- is halved and has its sign changed.
- is halved.
- has its sign changed.
- is unchanged.
Learn more about Hess' law here: https://brainly.com/question/11628413