The total number of molecules with zero dipole moment among $$\mathrm{CH}_4, \mathrm{BF}_3, \mathrm{H}_2 \mathrm{O}, \mathrm{HF}, \mathrm{NH}_3, \mathrm{CO}_2$$ and $\mathrm{SO}_2$ is ________.

<p>To determine which molecules have a zero dipole moment from the list provided, we need to consider their molecular geometry and symmetry. Molecules that are symmetrical often have zero dipole moment because the bond dipoles cancel each other out.</p> <p><p><strong>CO₂ (Carbon Dioxide)</strong>: This molecule is linear in shape. The two opposing oxygen atoms pull equally on the carbon, canceling out the dipoles, resulting in a net dipole moment of zero.</p></p> <p><p><strong>CH₄ (Methane)</strong>: Methane is tetrahedral and symmetrical, with all four hydrogen atoms equally spaced around the carbon atom. This symmetry leads to the cancellation of dipoles, giving a net dipole moment of zero.</p></p> <p><p><strong>BF₃ (Boron Trifluoride)</strong>: This molecule is trigonal planar and symmetrical. The three fluorine atoms are arranged evenly around the central boron atom, causing the dipoles to cancel each other out, resulting in a zero dipole moment.</p></p> <p>Therefore, the molecules with zero dipole moment among the list provided are CO₂, CH₄, and BF₃.</p>