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As for every pure element, the heat of formation of O is zero. That is because elements are the smallest constituents and are not made up of anything; therefore, no heat is needed to form pure elements from base substances, as there are no base substances to be used to form the pure elements.
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When does enthalpy become zero?
Enthalpy can be zero for a pure substance at its standard state, where it is defined as the enthalpy of formation. This typically occurs at a reference temperature and pressure specified for the substance.
What is the Delta H of Na?
The standard enthalpy change of formation of sodium (ΔHf°) is 0 kJ/mol. This means that the enthalpy change when 1 mole of sodium is formed from its elements in their standard state is zero.
What is the basic difference between enthalpy of formation?
Standard Heat (Enthalpy) of Formation, Hfo, of any compound is the enthalpy change of the reaction by which it is formed from its elements, reactants and products all being in a given standard state.By definition, the standard enthalpy (heat) of formation of an element in its standard state is zero, Hfo = 0.Standard Molar Enthalpy (Heat) of Formation, Hmo, of a compound is the enthalpy change that occurs when one mole of the compound in its standard state is formed from its elements in their standard states.Standard Enthalpy (Heat) of Reaction, Ho, is the difference between the standard enthalpies (heats) of formation of the products and the reactants.Ho(reaction) = the sum of the enthalpy (heat) of formation of products - the sum of the enthalpy (heat) of formation of reactants: Ho(reaction) = Hof(products) - Hof(reactants)To calculate an Enthalpy (Heat) of Reaction:Write the balanced chemical equation for the reaction Remember to include the state (solid, liquid, gas, or aqueous) for each reactant and product.Write the general equation for calculating the enthalpy (heat) of reaction: Ho(reaction) = Hof(products) - Hof(reactants)Substitute the values for the enthalpy (heat) of formation of each product and reactant into the equation. Remember, if there are 2 moles of a reactant or product, you will need to multiply the enthalpy term by 2, if molar enthalpies (heats) of formation are used.Standard Enthalpy (Heat) of FormationExample: Standard Enthalpy (Heat) of Formation of WaterThe standard enthalpy (heat) of formation for liquid water at 298K (25o) is -286 kJ mol-1. This means that 286 kJ of energy is released when liquid water, H2O(l), is produced from its elements, hydrogen and oxygen, in their standard states, ie, H2(g) and O2(g).This reaction is written as:H2(g) + ½O2(g) -----> H2O(l) Hfo = -286 kJ mol-1The standard enthalpy (heat) of formation of water vapour at 298K (25o) is -242 kJ mol-1.This means that 242 kJ of energy is released when gaseous water (water vapour), H2O(g), is produced from its elements, hydrogen and oxygen, in their standard states, ie, H2(g) and O2(g).This reaction is written as:H2(g) + ½O2(g) -----> H2O(g) Hfo = -242 kJ mol-1
Is the enthalpy of formation always negative?
No, the enthalpy of formation can be positive, negative, or zero, depending on the specific chemical reaction and the substances involved.
What is the stable state of an element?
The standard state, or reference state, of an element is defined as its thermodynamically most stable state at 1 bar at a given temperature (typically at 298.15 K). In thermochemistry, an element is defined to have an enthalpy of formation of zero in its standard state. For example, the reference state for carbon is graphite, because it is more stable than the other allotropes.
Why does oxygen gas not have an enthalpy of formation but ozone does?
Oxygen gas (O2) does not have an enthalpy of formation because it is an element in its standard state, which has an enthalpy of formation of zero by definition. Ozone (O3), on the other hand, is a compound and has a defined enthalpy of formation because it is formed from its elements in their standard states.
When does enthalpy become zero?
Enthalpy can be zero for a pure substance at its standard state, where it is defined as the enthalpy of formation. This typically occurs at a reference temperature and pressure specified for the substance.
What is the Delta H of Na?
The standard enthalpy change of formation of sodium (ΔHf°) is 0 kJ/mol. This means that the enthalpy change when 1 mole of sodium is formed from its elements in their standard state is zero.
What is the basic difference between enthalpy of formation?
Standard Heat (Enthalpy) of Formation, Hfo, of any compound is the enthalpy change of the reaction by which it is formed from its elements, reactants and products all being in a given standard state.By definition, the standard enthalpy (heat) of formation of an element in its standard state is zero, Hfo = 0.Standard Molar Enthalpy (Heat) of Formation, Hmo, of a compound is the enthalpy change that occurs when one mole of the compound in its standard state is formed from its elements in their standard states.Standard Enthalpy (Heat) of Reaction, Ho, is the difference between the standard enthalpies (heats) of formation of the products and the reactants.Ho(reaction) = the sum of the enthalpy (heat) of formation of products - the sum of the enthalpy (heat) of formation of reactants: Ho(reaction) = Hof(products) - Hof(reactants)To calculate an Enthalpy (Heat) of Reaction:Write the balanced chemical equation for the reaction Remember to include the state (solid, liquid, gas, or aqueous) for each reactant and product.Write the general equation for calculating the enthalpy (heat) of reaction: Ho(reaction) = Hof(products) - Hof(reactants)Substitute the values for the enthalpy (heat) of formation of each product and reactant into the equation. Remember, if there are 2 moles of a reactant or product, you will need to multiply the enthalpy term by 2, if molar enthalpies (heats) of formation are used.Standard Enthalpy (Heat) of FormationExample: Standard Enthalpy (Heat) of Formation of WaterThe standard enthalpy (heat) of formation for liquid water at 298K (25o) is -286 kJ mol-1. This means that 286 kJ of energy is released when liquid water, H2O(l), is produced from its elements, hydrogen and oxygen, in their standard states, ie, H2(g) and O2(g).This reaction is written as:H2(g) + ½O2(g) -----> H2O(l) Hfo = -286 kJ mol-1The standard enthalpy (heat) of formation of water vapour at 298K (25o) is -242 kJ mol-1.This means that 242 kJ of energy is released when gaseous water (water vapour), H2O(g), is produced from its elements, hydrogen and oxygen, in their standard states, ie, H2(g) and O2(g).This reaction is written as:H2(g) + ½O2(g) -----> H2O(g) Hfo = -242 kJ mol-1
Is the enthalpy of formation always negative?
No, the enthalpy of formation can be positive, negative, or zero, depending on the specific chemical reaction and the substances involved.
What is the standard enthalpy of formation of hydrogen bromide?
[from wikipedia] The standard enthalpy of formation"standard heat of formation" of a compound is the change of enthalpy that accompanies the formation of 1 mole of a substance in its standard state from its constituent elements in their standard states (the most stable form of the element at 1 bar of pressure and the specified temperature, usually 298.15 K or 25 degrees Celsius). Its symbol is ΔHfO.
What is the standard heat of formation of a free element in its standard state?
The standard heat of formation of a free element in its standard state is defined as zero. This is because it is the reference point from which the heat of formation of other compounds is determined.
What is the formula for finding heat formation?
Heat of combustion of a hydrocarbon is based on the reaction: fuel + oxygen --> carbon dioxide + water (unless you have some nitrogen or sulfur in the fuel, in which case it gets a little more complex) The heat of formation of O2 is zero (O2 is the reference state) The heat of formation of CO2 is the same as the heat of combustion for carbon The heat of formation of H2O is the same as the heat of combustion for hydrogen To find the heat of formation of the fuel, you subtract the heat of combustion from the heats of formation - (weighted with the stoichiometric coefficients from the balanced reaction equation).
How would an oxygen atom become O-2?
An oxygen atom would become O-2 by sharing two electrons with another oxygen atom, forming a stable oxygen molecule. This sharing of electrons creates a double bond between the two oxygen atoms, resulting in the formation of a molecule with a net charge of zero.
What is the stable state of an element?
The standard state, or reference state, of an element is defined as its thermodynamically most stable state at 1 bar at a given temperature (typically at 298.15 K). In thermochemistry, an element is defined to have an enthalpy of formation of zero in its standard state. For example, the reference state for carbon is graphite, because it is more stable than the other allotropes.
Is oxygen warm?
Oxygen can be at any temperature from absolute zero to millions of degrees.
How much oxygen does hot water have?
zero
