1. What is Enthalpy of Formation?

The enthalpy of formation (ΔHf) is the change in enthalpy when one mole of a compound is formed from its elements in their standard states. For methane (CH₄), it represents the energy change when carbon and hydrogen combine to form one mole of methane.

2. How Does the Calculator Work?

The calculator uses the enthalpy of formation equation:

For the formation of methane (CH₄) from its elements:

• \( C + 2H_2 \rightarrow CH_4 \)
• \( \Delta H_f = \Delta H_f(CH_4) - [\Delta H_f(C) + 2 \times \Delta H_f(H_2)] \)

Explanation: The equation calculates the energy difference between the products and reactants in their standard states.

3. Importance of Enthalpy Calculations

Details: Enthalpy of formation values are crucial for predicting whether reactions will be exothermic or endothermic, and for calculating energy changes in chemical processes.

4. Using the Calculator

Tips: Enter standard enthalpy of formation values for carbon, hydrogen, and methane in kJ/mol. The calculator will compute the enthalpy change for the formation reaction.

5. Frequently Asked Questions (FAQ)

Q1: What are standard conditions for ΔHf?
A: Standard conditions are 1 atm pressure and usually 25°C (298 K), with all substances in their standard states.

Q2: Why is ΔHf for elements in their standard state zero?
A: By definition, the enthalpy of formation of an element in its most stable form is zero under standard conditions.

Q3: What is the standard ΔHf for methane?
A: The standard enthalpy of formation for methane is -74.6 kJ/mol at 298 K.

Q4: How does temperature affect ΔHf?
A: ΔHf values are temperature-dependent, but standard values are typically reported at 298 K.

Q5: Can this be used for other compounds?
A: Yes, the same principle applies to any compound, but you must use the correct stoichiometric coefficients.