What do you mean by standard enthalpy of formation?
The standard enthalpy of formation of a compound is the enthalpy change that occurs when 1 mole of the compound is formed from its constituent elements in their standard states. A pure element in its standard state has a standard enthalpy of formation of zero.
Which substances have a standard enthalpy of formation of zero?
All elements in their standard states (oxygen gas, solid carbon in the form of graphite, etc.) have a standard enthalpy of formation of zero, as there is no change involved in their formation.
What is the heat of combustion of dodecane?
7901.74 kJ mol
Dodecane
| Names | |
|---|---|
| Heat capacity (C) | 376.00 J K−1 mol−1 |
| Std molar entropy (So298) | 490.66 J K−1 mol−1 |
| Std enthalpy of formation (ΔfH⦵298) | −353.5–−350.7 kJ mol−1 |
| Std enthalpy of combustion (ΔcH⦵298) | −7901.74 kJ mol−1 |
What is the enthalpy of O2?
Selected ATcT enthalpy of formation based on version 1.122 of the Thermochemical Network
| Species Name | Formula | ΔfH°(298.15 K) |
|---|---|---|
| Dioxygen | O2 (g, singlet) | 94.383 |
What is standard enthalpy of formation with example?
The standard enthalpy of formation of any element in its standard state is zero by definition. For example, although oxygen can exist as ozone (O3), atomic oxygen (O), and molecular oxygen (O2), O2 is the most stable form at 1 atm pressure and 25°C. Similarly, hydrogen is H2(g), not atomic hydrogen (H).
What is standard enthalpy of formation class 11?
Standard enthalpy of formation of a substance is defined as the enthalpy change accompanying the formation of 1 mole of the substance in the standard state from its elements, also taken in the standard state. It is usually represented ΔfH°.
What is the density of dodecane?
750 kg/m³
Dodecane/Density
Why is oxygen standard enthalpy of formation?
The enthalpy of formation for an element in its elemental state will always be 0 because it takes no energy to form a naturally-occurring compound. We can only measure changes in enthalpy. Now, the enthalpy change for a formation reaction is called enthalpy of formation.
Why is the standard enthalpy of O2 zero?
Also notice in Appendix A that the standard enthalpy of formation of O 2(g) is zero because it is the most stable form of oxygen in its standard state. For the formation of each compound, write a balanced chemical equation corresponding to the standard enthalpy of formation of each compound.
What is the standard enthalpy of formation in chemistry?
Standard Enthalpy of Formation or Standard Heat of Formation. Formation of the compound is an endothermic reaction. ΔH fo = – (a negative value) Overall, energy is released when the elements in their standard states form the compound. Formation of the compound is an exothermic reaction.
What is the enthalpy change required to produce NH 4?
The enthalpy change required to produce the elements hydrogen, nitrogen and chlorine in their standard states is the sum of the enthalpy change for breaking apart hydrogen chloride molecules and for breaking apart ammonia molecules: Now we can use this H 2 (g), Cl 2 (g) and N 2 (g) to produce NH 4 Cl (s) .
Which is the standard heat of formation of a compound?
Standard Heat of Formation (standard enthalpy of formation), ΔHfo, of any compound is defined as the enthalpy change of the reaction by which it is formed from its elements in their standard state.
What is the standard enthalpy of ammonium chloride?
From the table of values for Standard Enthalpy of Formation at 25°C given in the previous section, we find that the standard enthalpy of formation of ammonium chloride (NH 4 Cl (s)) is -314.4 kJ mol -1.