Calculate the standard internal energy change for the formation of water at 298K. The standard enthalpy of formation of water at 298K is - 285.8 KJ/mol.
To calculate the standard internal energy change for the formation of water at 298K, you can use the equation:
ΔU = ΔH - ΔnRT
where:
- ΔU is the standard internal energy change
- ΔH is the standard enthalpy change
- Δn is the change in the number of moles of gas
- R is the ideal gas constant (8.314 J/mol·K)
- T is the temperature in Kelvin (298K)
In this case, we are forming water, which is a liquid at room temperature. Therefore, there is no change in the number of moles of gas (Δn = 0).
Now, let's plug the values into the equation:
ΔU = - 285.8 KJ/mol - (0) - (8.314 J/mol·K)(298K)
Note: We need to convert the enthalpy change from kilojoules per mole to joules per mole by multiplying by 1000.
ΔU = - 285,800 J/mol - (0) - (8.314 J/mol·K)(298K)
Simplifying further, we have:
ΔU = - 285,800 J/mol - 2473.372 J/mol
ΔU = - 288,273.372 J/mol
Therefore, the standard internal energy change for the formation of water at 298K is approximately -288,273.372 J/mol.