# Calculate \DeltarH0 and \DeltarU0 for Hydrogenation of Ethyne to Ethene at 348 K

• winterwind
In summary, the problem asks to calculate \DeltarH0 and \DeltarU0 at 348 K for the hydrogenation of ethyne to ethene using data from Tables 2.5 and 2.7. Hess's Law and Kirchhoff's Law can be used to combine equations and find the values at 348 K. The relationship between \DeltarU0 and enthalpy values can be found using the equation \DeltaH=\DeltaU+\DeltangasRT.
winterwind

## Homework Statement

Calculate $$\Delta$$rH0 and $$\Delta$$rU0 at 348 K for the hydrogenation of ethyne (acetylene) to ethene (ethylene) from the enthalpy of combustion and heat capacity data in Tables 2.5 and 2.7. Assume the heat capacaties to be constant over the temperature range involved.

$$\Delta$$fH0 of ethyne = +226.73 kJ/mol
$$\Delta$$p,mC0 of ethyne = 43.93

$$\Delta$$fH0 of ethene = +52.26 kJ/mol
$$\Delta$$p,mC0 of ethene = 43.56

Other relevant data in the tables are also given, such as Enthalpy of fusion, enthaply of combustion, molar heat capacity, Benson thermochemical groups, of various molecules, including water, oxidation, hydrogen gas, carbon dioxide gas, ethane, ethene, and ethyne.
I only included the above because I think I would need to use those for sure. The other data can be easily found.

Hess's Law
Kirchhoff's Law

## The Attempt at a Solution

I might try combining equations to arrive at the right equation (Hess's Law). Maybe Kirchoff's Law to find the values at 348 K? What is meant by $$\Delta$$rU0? Is this the change in internal energy? How does it relate to enthalpy (fusion, heat capacity, etc.)?

Thanks!

EDIT: I only need help with question in post #2 now. I figured out the other parts already.

Last edited:
I just need help with this part of the probelem now:

Calculate $$\Delta$$rU0 at 298 K for the hydrogenation of ethyne (acetylene) to ethene (ethylene) from the enthalpy of combustion and heat capacity data in Tables 2.5 and 2.7. Assume the heat capacaties to be constant over the temperature range involved.

I figured out the other parts of the problem. I am still not sure of the relationship between $$\Delta$$rU0 and enthalpy values.

Hi winterwind,
I'm also working on this problem for a homework due this week...which makes me wonder...

Anyway, I found in my notes that $$\Delta$$H=$$\Delta$$U+$$\Delta$$ngasRT.

I hope this helps :)

## 1. What is thermochemistry?

Thermochemistry is the branch of science that studies the relationship between heat and chemical reactions. It involves the measurement and calculation of the energy changes that occur during a chemical reaction.

## 2. How do you solve thermochemistry problems?

To solve a thermochemistry problem, you must first identify the given information and what is being asked. Then, use the appropriate formula to calculate the energy change, taking into account the sign conventions and units. Finally, check your answer for reasonableness and accuracy.

## 3. What is an endothermic reaction?

An endothermic reaction is a chemical reaction that absorbs heat from its surroundings. This results in a decrease in temperature of the surroundings. The energy of the products is greater than the energy of the reactants, so the reaction is said to be endothermic.

## 4. What is an exothermic reaction?

An exothermic reaction is a chemical reaction that releases heat to its surroundings. This results in an increase in temperature of the surroundings. The energy of the products is less than the energy of the reactants, so the reaction is said to be exothermic.

## 5. How is enthalpy related to thermochemistry?

Enthalpy is a thermodynamic property that represents the total energy of a system. In thermochemistry, enthalpy change (ΔH) is used to measure the heat absorbed or released during a chemical reaction. It is related to the internal energy (ΔU) and pressure-volume work (PΔV) of the system through the equation ΔH = ΔU + PΔV.

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