How many moles of hydrogen are required to completely hydrogenate one mole of pent-1-en-3-yne?

1 answer

Pent-1-en-3-yne has a triple bond and a double bond, so it can be hydrogenated to pentane by adding six moles of hydrogen gas (H2). Each double bond requires one mole of hydrogen gas to break the bond and form two single C-H bonds. Each triple bond requires two moles of hydrogen gas to break the bond and form two single C-H bonds and one single C-C bond.

Therefore, to hydrogenate one mole of pent-1-en-3-yne to pentane, we need:

- 3 moles of hydrogen gas for the triple bond (2 moles for each triple bond x 1 triple bond)
- 2 moles of hydrogen gas for the double bond (1 mole for each double bond x 2 double bonds)
- Total: 3 + 2 = 5 moles of hydrogen gas

Therefore, 5 moles of hydrogen gas are required to completely hydrogenate one mole of pent-1-en-3-yne.