Which of the following incorrectly assigns a dipole moment to a bond?

• A. The N–O bond in nitric oxide (NO) has a dipole moment.
• B. The O–H bond in water (H_2O) has a dipole moment.
• C. The C–H bond in methane (CH_4) has a significant dipole moment.
• D. The H–F bond in hydrogen fluoride (HF) has a large dipole moment.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand what a dipole moment is. A dipole moment arises in a bond when there is a difference in electronegativity between the two atoms, causing an uneven distribution of electron density and resulting in a partial positive and partial negative end.
2. Step 2: Analyze the bonds given in the problem by comparing the electronegativities of the atoms involved. For example, in the N–O bond, nitrogen and oxygen have different electronegativities, so this bond has a dipole moment.
3. Step 3: Consider the O–H bond in water. Oxygen is more electronegative than hydrogen, so the bond is polar and has a dipole moment.
4. Step 4: Evaluate the C–H bond in methane. Carbon and hydrogen have very similar electronegativities, so the bond is essentially nonpolar and does not have a significant dipole moment. This is the incorrect assignment mentioned in the problem.
5. Step 5: Look at the H–F bond in hydrogen fluoride. Fluorine is highly electronegative compared to hydrogen, so this bond has a large dipole moment.