Which of the following molecules contain polar covalent bonds: CO, N2, NH3, NH4+, and HCl?

To determine which of the given molecules contain polar covalent bonds, we need to understand what a polar covalent bond is. A polar covalent bond is a type of chemical bond where a pair of electrons is unequally shared between two atoms. This is usually due to one atom having higher electronegativity than the other, causing electrons to spend more time closer to the atom with higher electronegativity.

1. CO (Carbon Monoxide): Carbon and Oxygen have different electronegativities (C: 2.55, O: 3.44). Therefore, the bond between them is polar covalent.

2. N2 (Nitrogen Gas): This molecule consists of two Nitrogen atoms. Since they have the same electronegativity, the bond between them is nonpolar covalent, not polar covalent.

3. NH3 (Ammonia): Nitrogen and Hydrogen have different electronegativities (N: 3.04, H: 2.20). Therefore, the bonds between them are polar covalent.

4. NH4+ (Ammonium): This is a polyatomic ion, but it still contains polar covalent bonds. The bonds between Nitrogen and Hydrogen are polar covalent due to their different electronegativities.

5. HCl (Hydrochloric Acid): Hydrogen and Chlorine have different electronegativities (H: 2.20, Cl: 3.16). Therefore, the bond between them is polar covalent.

So, the molecules CO, NH3, NH4+, and HCl contain polar covalent bonds.