To determine which compound contains both sigma and pi bonds, let's analyze the bonding in each of the given compounds.
1. HCCl₃ (Chloroform):
- The molecule HCCl₃ consists of a central carbon atom bonded to one hydrogen atom and three chlorine atoms.
- Carbon forms a single bond (sigma bond) with each chlorine and hydrogen atom.
- All bonds in HCCl₃ are sigma bonds.
- Thus, HCCl₃ contains only sigma bonds.
2. H₂CO (Formaldehyde):
- The molecule H₂CO consists of a central carbon atom bonded to two hydrogen atoms and one oxygen atom.
- Carbon forms single bonds (sigma bonds) with the two hydrogen atoms.
- Between carbon and oxygen, there is a double bond. A double bond consists of one sigma bond and one pi bond.
- Hence, H₂CO contains both sigma and pi bonds.
3. H₂S (Hydrogen sulfide):
- The molecule H₂S consists of a central sulfur atom bonded to two hydrogen atoms.
- Sulfur forms single bonds (sigma bonds) with each hydrogen atom.
- All bonds in H₂S are sigma bonds.
- Thus, H₂S contains only sigma bonds.
4. HBr (Hydrogen bromide):
- The molecule HBr consists of a single bond between hydrogen and bromine.
- Single bonds are sigma bonds.
- Thus, HBr contains only a sigma bond.
After analyzing all the compounds, we find that H₂CO (Formaldehyde) contains both sigma and pi bonds. The double bond between carbon and oxygen in formaldehyde includes one sigma bond and one pi bond.
Thus, the compound that contains both sigma and pi bonds is:
[tex]\[ \boxed{H_2CO} \][/tex]
