which compound contains both sigma and pi bonds?\no hccl3\no h2co\no h2s\no hbr

Explanation:

Step1: Recall bond - type rules

Single bonds are sigma bonds. Double bonds consist of one sigma and one pi bond. Triple bonds have one sigma and two pi bonds.

Step2: Analyze each compound

• In $HCCl_3$, all bonds are single bonds (C - H and C - Cl are single bonds), so it has only sigma bonds.
• In $H_2CO$, the carbon - oxygen bond is a double bond (C=O) and the C - H bonds are single bonds. The C - H single bonds are sigma bonds, and the C=O double bond has one sigma and one pi bond.
• In $H_2S$, the S - H bonds are single bonds, so it has only sigma bonds.
• In $HBr$, the H - Br bond is a single bond, so it has only sigma bonds.

Answer:

B. $H_2CO$