i need help with the below question, i have tried answering it, but do not know where to go after the equations, please start me off on how to find the enthalpy of combustion of at least one....
Consider methane, CH4, and hydrogen, H2, as possible fuel sources.
(a) Write the chemical equation for the complete combustion of each fuel. Then find the enthalpy of combustion, ΔHcomb, of each fuel. Express your answers in kJ/mol and kJ/g. Assume that water vapour, rather than liquid water, is formed in both reactions.
CH4 + 2O2 ↔ 2H2O + CO2
2H2 + O2 ↔ 2H2O
should i use the enthalpy of formations and its equations??
i tried using it for CH4, below is my working am i correct? cause i researched a website(cannot post link)
and it uses enthalpy of formation!!!
i am using the molar enthalpy of formation equation:
(ndeltaHf products) - (ndeltaHf reactants)
CH4 + 2O2 ↔ 2H2O + CO2
deltaCOMB = [(2*-241.8)+(-393.5)]-[-74.6]
=-502.5kJ
Yes, that's the way to go with the CH4. My set of tables gave -74.81 kJ/mol for CH4 but use what you have in your tables. Just check them to make sure the numbers are right. The -502.5 kJ (I didn't check the math) is kJ/mol. To convert to grams you multiply by molar mass CH4.
For H2 use
2H2 + O2 ==> 2H2O. Remember H2 and O2 will be zero since they are in their "standard" state.
To find the enthalpy of combustion for each fuel, you can indeed use the enthalpy of formation values.
The enthalpy of combustion (ΔHcomb) can be calculated using the following equation:
ΔHcomb = ∑(ΔHf products) - ∑(ΔHf reactants)
(a) Let's start with methane, CH4. The balanced chemical equation for the complete combustion of methane is:
CH4 + 2O2 → 2H2O + CO2
1. Find the enthalpy of formation (ΔHf) values for the reactants and products. The ΔHf of methane (CH4) is -74.8 kJ/mol, the ΔHf of water (H2O) is -285.8 kJ/mol, and the ΔHf of carbon dioxide (CO2) is -393.5 kJ/mol.
2. Next, substitute the values into the equation:
ΔHcomb(CH4) = (2 × ΔHf(H2O)) + ΔHf(CO2) - ΔHf(CH4)
3. Calculate the enthalpy of combustion:
ΔHcomb(CH4) = (2 × -285.8 kJ/mol) + (-393.5 kJ/mol) - (-74.8 kJ/mol)
(b) Now consider hydrogen gas, H2. The balanced chemical equation for the complete combustion of hydrogen is:
2H2 + O2 → 2H2O
1. Find the enthalpy of formation (ΔHf) values for the reactants and products. The ΔHf of water (H2O) is -285.8 kJ/mol and the ΔHf of hydrogen (H2) is 0 kJ/mol.
2. Substitute the values into the equation:
ΔHcomb(H2) = (2 × ΔHf(H2O)) - ΔHf(H2)
3. Calculate the enthalpy of combustion:
ΔHcomb(H2) = (2 × -285.8 kJ/mol) - 0 kJ/mol
By following these steps, you should be able to find the enthalpy of combustion for methane and hydrogen.
To find the enthalpy of combustion, you can use the concept of the enthalpy of formation and the standard enthalpy of reactions.
The enthalpy of formation (ΔHf) is the change in enthalpy that accompanies the formation of one mole of a compound from its constituent elements in their standard states.
The standard enthalpy of reaction (ΔHrxn) is the enthalpy change that occurs when the reactants in their standard states are converted into products in their standard states, with all reactants and products at the same temperature and pressure.
In this case, you have the chemical equations for the complete combustion of two fuels: methane (CH4) and hydrogen (H2).
1. Methane (CH4):
The balanced chemical equation for the combustion of methane is:
CH4 + 2O2 ↔ 2H2O + CO2
To find the enthalpy of combustion (ΔHcomb) of methane, you can utilize the enthalpy of formation values for methane (ΔHf(CH4)), water (ΔHf(H2O)), and carbon dioxide (ΔHf(CO2)).
The formula to calculate ΔHcomb is:
ΔHcomb = ∑ (ΔHf(products)) - ∑ (ΔHf(reactants))
2. Hydrogen (H2):
The balanced chemical equation for the combustion of hydrogen is:
2H2 + O2 ↔ 2H2O
To find the enthalpy of combustion (ΔHcomb) of hydrogen, you can again use the enthalpy of formation values for water (ΔHf(H2O)).
Similarly, the formula to calculate ΔHcomb is:
ΔHcomb = ∑ (ΔHf(products)) - ∑ (ΔHf(reactants))
To find the enthalpy of combustion expressed in kJ/g, you will also need the molar mass of the fuel.
By substituting the appropriate values into the equations, you can calculate the enthalpy of combustion for both methane and hydrogen.