calculate the standard enthalpy change for each of the following reactions. N2O4(g)+4H2(g)=N2(g)+4H2O(g)
To calculate the standard enthalpy change (∆H) for a reaction, we need to use the standard enthalpies of formation (∆Hf) for each component involved.
The standard enthalpy of formation is the enthalpy change that takes place when one mole of a compound is formed from its elements in their standard states at a given temperature and pressure.
Using the given reaction: N2O4(g) + 4H2(g) = N2(g) + 4H2O(g)
We can calculate the overall ∆H by using the following equation:
∆H = Σ n * ∆Hf(products) - Σ n * ∆Hf(reactants)
where Σ n means the sum of the coefficients of each component in the reaction.
Now, let's find the standard enthalpy of formation values for each compound involved:
∆Hf(N2O4) = 9.16 kJ/mol
∆Hf(N2) = 0 kJ/mol (standard state)
∆Hf(H2) = 0 kJ/mol (standard state)
∆Hf(H2O) = -285.8 kJ/mol (standard state)
Next, we calculate the enthalpy change:
∆H = (1 * ∆Hf(N2)) + (4 * ∆Hf(H2O)) - (1 * ∆Hf(N2O4)) - (4 * ∆Hf(H2))
∆H = (1 * 0 kJ/mol) + (4 * -285.8 kJ/mol) - (1 * 9.16 kJ/mol) - (4 * 0 kJ/mol)
∆H = -1143.2 kJ/mol - 9.16 kJ/mol
∆H = -1152.36 kJ/mol
Therefore, the standard enthalpy change (∆H) for the given reaction is -1152.36 kJ/mol.
To calculate the standard enthalpy change (ΔH°) for a given reaction, we need to use the standard enthalpies of formation (ΔHf°) for each compound involved. The standard enthalpy of formation is the change in enthalpy that occurs when one mole of a compound is formed from its constituent elements, with all reactants and products in their standard states.
Here's how you can calculate the standard enthalpy change for the given reaction:
1. Look up the standard enthalpies of formation (ΔHf°) for each compound involved in the reaction. You can find these values in reference books or online resources.
- N2O4(g): Let's assume its ΔHf° is x kJ/mol.
- H2(g): The standard enthalpy of formation for hydrogen gas is usually defined as zero, since it is used as a reference point.
- N2(g): Assume its ΔHf° is y kJ/mol.
- H2O(g): Assume its ΔHf° is z kJ/mol.
2. Write down the balanced chemical equation for the reaction:
N2O4(g) + 4H2(g) → N2(g) + 4H2O(g)
3. Calculate the standard enthalpy change (ΔH°) for the reaction using the following equation:
ΔH° = Σ(ΔHf° products) - Σ(ΔHf° reactants)
ΔH° = [y + 4z] - [x + 4(0)]
ΔH° = y + 4z - x
Therefore, the standard enthalpy change (ΔH°) for the reaction N2O4(g) + 4H2(g) → N2(g) + 4H2O(g) is (y + 4z - x) kJ/mol. The specific numerical value depends on the given standard enthalpies of formation for N2O4, N2, and H2O that you obtain from your reference sources.
dH = delta H.
dHrxn = (n*dHo products) - (n*dHo reactants)