Using the heats of formation, determine what the heat of vaporization of water should be.
Heat of formation of water: -248.8 kJ/mol
The chemical reaction:
2CH4 + 3O2 => 2CO + 4H2O (balanced)
To determine the heat of vaporization of water, we'll need to use the given heat of formation of water and the enthalpy change in the reaction for converting water from its liquid phase to its gaseous phase.
1. First, let's determine the enthalpy change for the reaction given:
2CH4 + 3O2 => 2CO + 4H2O
From the balanced equation, we can see that 4 moles of water are produced for every 2 moles of CH4 (methane) reacted. Therefore, the enthalpy change in the reaction for the formation of 4 moles of water will be twice the enthalpy change for one mole of methane.
2. The enthalpy change for the reaction can be calculated using the heat of formation values:
ΔHrxn = Σ(Hf(products)) - Σ(Hf(reactants))
The heat of formation for CO is -110.5 kJ/mol, and the heat of formation for CH4 is -74.8 kJ/mol. Plugging in these values, we can calculate the enthalpy change for the reaction:
ΔHrxn = (2 × (-110.5 kJ/mol)) - (2 × (-74.8 kJ/mol))
= -221 kJ/mol + 149.6 kJ/mol
= -71.4 kJ/mol
3. Now, let's determine the enthalpy change for the vaporization of water:
The balanced equation shows that 4 moles of water are formed in the reaction. Therefore, the enthalpy change for 4 moles of water vaporizing will be four times the enthalpy change calculated in step 2.
ΔHvap = 4 × ΔHrxn
= 4 × (-71.4 kJ/mol)
= -285.6 kJ/mol
Therefore, the heat of vaporization of water should be approximately -285.6 kJ/mol.
To determine the heat of vaporization of water using heats of formation, we can follow these steps:
1. Write out the balanced chemical equation for the vaporization of water:
H2O(l) => H2O(g)
2. Calculate the change in enthalpy (ΔH) for the reaction using the heat of formation values:
ΔH = ΣΔHf(products) - ΣΔHf(reactants)
Since we only have one product and one reactant, the equation simplifies to:
ΔH = ΔHf(H2O(g)) - ΔHf(H2O(l))
3. Look up the values of the heat of formation for both water in the respective phases and substitute them into the equation:
ΔH = ΔHf(H2O(g)) - ΔHf(H2O(l))
On the given information, you have the heat of formation of water in the liquid phase, which is -248.8 kJ/mol. Unfortunately, the heat of formation of water in the gas phase is not provided. Therefore, we cannot directly calculate the heat of vaporization of water using this method.
4. To determine the heat of vaporization of water, alternative methods, such as using experimental data or equations, need to be employed.