Is the formation of C2H2 endothermic or exothermic?

The formation of C2H2 is endothermic as it absorbs heat.

If you go on your chemistry reference sheet we could see that positive delta H on table I indicates a endothermic reaction which means that energy is absorbed.

The formation of C2H2, which is the chemical formula for acetylene, is an exothermic process. This means that it releases heat energy when the reaction occurs.

To determine whether the formation of C2H2 (also known as acetylene) is endothermic or exothermic, we can refer to the concept of bond energies.

Bond formation involves breaking existing bonds and forming new ones. When a chemical bond is broken, energy is required, which is an endothermic process. Conversely, when a chemical bond is formed, energy is released, which is an exothermic process.

To find the answer, we need to compare the bond energies of the reactants (carbon-carbon and carbon-hydrogen bonds) with the bond energies of the products (carbon-carbon and carbon-hydrogen triple bond).

The bond energy of a carbon-carbon double bond is approximately 615 kJ/mol, while the bond energy of a carbon-hydrogen single bond is about 410 kJ/mol. On the other hand, the bond energy of a carbon-carbon triple bond is approximately 840 kJ/mol, and the bond energy of a carbon-hydrogen bond in the acetylene molecule is approximately 310 kJ/mol.

Now, let's calculate the energy change during the formation of C2H2:

Reactants:
- Carbon-carbon double bond (615 kJ/mol)
- Carbon-hydrogen single bond (410 kJ/mol)

Products:
- Carbon-carbon triple bond (840 kJ/mol)
- Carbon-hydrogen bond in C2H2 (310 kJ/mol)

Energy change = (Energy of bonds broken) - (Energy of bonds formed)
Energy change = ((615 kJ/mol) + (410 kJ/mol)) - ((840 kJ/mol) + (310 kJ/mol))
Energy change = 1025 kJ/mol - 1150 kJ/mol
Energy change = -125 kJ/mol

Since the energy change is negative (-125 kJ/mol), it indicates that the formation of C2H2 is exothermic. This means that the process releases energy during the formation of the acetylene molecule.

Look it up in the tables, dHo formation C2H2.