# Heat enthelpy of molecular hydrogen

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In summary, to find the energy needed to dissociate a single H2 molecule in electron-volts, you must first find the enthalpy of formation of atomic hydrogen, which is the enthalpy change when a mole of atomic hydrogen is formed by dissociating 1/2 mole of molecular hydrogen. Using the equation delta(U) = delta(H) - P*delta(V), and given values of delta(H) = -217.97 kJ and P*delta(V) = 2.5 kJ, we find that delta(U) = -220.5 kJ. This value needs to be doubled and converted to electron-volts to find the energy needed to dissociate a single H2 molecule, which

## Homework Statement

Look up the enthalpy of formation of atomic hydrogen in the back of the book. This is the enthalpy change when a mole of atomic hydrogen is formed by dissociating 1/2 mole of molecular hydrogen (the more stable state of the element). From this number, determinethe energy needed to dissociate a single H2 molecule , in electron-volts.

## Homework Equations

PV=3100 J
delta(H)=delta(U)+P*delta(V)
H=U+PV

## The Attempt at a Solution

find delta(U)
delta(U)=delta(H)-P*delta(V)

found delta(H) to be delta(H)=-217.97 kJ

According to the standard table T=298 K and P=1 bar=1atm?
R=8.31 J/K

PV=RT=(8.31 J/K)(298 K)=2.5 kJ

H-PV=(-217.97 kJ)-(2.5 kJ)=-220.5 kJ

Did I find delta(U) correctly?

This is the enthalpy of formation of atomic hydrogen, so the answer needs to be doubled (then the units changed to eV).

## 1. What is heat enthalpy of molecular hydrogen?

The heat enthalpy of molecular hydrogen (H2) is the amount of heat energy required to raise the temperature of one mole of H2 by one degree Celsius at constant pressure.

## 2. How is heat enthalpy of molecular hydrogen determined?

The heat enthalpy of molecular hydrogen is determined experimentally by measuring the heat flow into or out of a system during a chemical reaction or phase change involving H2.

## 3. What is the significance of heat enthalpy of molecular hydrogen?

The heat enthalpy of molecular hydrogen is an important thermodynamic property that helps in predicting the energy changes in reactions involving H2. It also plays a role in the design and optimization of hydrogen-based energy systems.

## 4. Does the heat enthalpy of molecular hydrogen change with temperature?

Yes, the heat enthalpy of molecular hydrogen is temperature-dependent. It increases with increasing temperature, as more energy is required to raise the temperature of H2 molecules.

## 5. How is the heat enthalpy of molecular hydrogen related to its enthalpy of formation?

The heat enthalpy of molecular hydrogen is the difference between the enthalpy of the products and the enthalpy of the reactants in a reaction involving H2. This difference is known as the enthalpy of formation of H2 and is a measure of the stability of H2 molecules in a reaction.