Question

Is O2 always a double bond?

In the question about Bond Enthalpy it is 2H2O2 → 2H2O + O2

In the answers O-O is a double bond. How do I find out if something has a double bond without looking at the answers?

Answer 1

BRINCLHOF

Br

I

N

Cl

H

O

F

all have dounle bonds.

You could also do lewis structures for each molecule to figure out the structure.

Answer 2

• O-O single bonds and H-O single bonds in
  `\text{H}_2\text{O}_2` molecules.
• H-O single bonds in
  `\text{H}_2\text{O}` molecules.
• O=O double bonds in
  `\text{O}_2` molecules.

Step-by-step explanation

How many valence electrons do atoms in each molecule need for them to be stable?

• Each H atom needs two valence electrons to be stable.
• Each atom of an element other than H needs eight valence electron to be stable.

• There are two H atoms and two O atoms in an
  `\text{H}_2\text{O}_2` molecule. Atoms in each
  `\text{H}_2\text{O}_2` need
  `2 * 1 + 2* 2 = 6` more electrons to be stable.
• There are two H atoms and one O atom in an
  `\text{H}_2\text{O}` molecule. Atoms in each
  `\text{H}_2\text{O}` molecule need
  `2 * 1 + 2= 4` more electrons to be stable.
• There are two O atoms in an
  `\text{O}_2` molecule. Atoms in each
  `\text{O}_2` molecule need
  `2 * 2 = 4` more electrons to be stable.

How many chemical bonds in each molecule?

Each chemical bond adds one valence electron to each bonding atom. Each chemical bond connects two atoms. As a result, each chemical bond adds two valence electrons to the molecule.

• Each
  `\text{H}_2\text{O}_2` molecule needs
  `6 / 2 = 3` chemical bonds.
• Each
  `\text{H}_2\text{O}` molecule needs
  `4 / 2 = 2` chemical bonds.
• Each
  `\text{O}_2` molecule needs
  `4 /2= 2` chemical bonds.

What chemical bonds are these? Again, each H atom needs only one more valence electron to be stable. It will share only one electron with O and form one H-O bond. The rest of the chemical bonds are between O atoms.

• There are two H atoms in each
  `\text{H}_2\text{O}_2` molecule, which form two H-O bonds. Two of the three chemical bonds in this molecule are H-O. The other is an O-O single bond between the two O atoms.
• There are two H atoms in each
  `\text{H}_2\text{O}` molecule, which form two H-O bonds. Both chemical bonds in this molecule are H-O. There's no O-O bond in this molecule.
• There is no H atom in
  `\text{O}_2` molecules. Both chemical bonds are between O atoms. However, there are only two O atoms. There must be two chemical bonds between the two O atoms. That bond will be an O-O double bond.