How many of the following molecules are with non-zero net dipole moment,
$$NH_3$$, HCl, $$H_2O$$, $$BeF_2$$, $$BH_3$$, $$CCl_4$$

We need to determine which of the given molecules have a non-zero net dipole moment.

Analyzing each molecule:

1. $$NH_3$$ (Ammonia): Trigonal pyramidal geometry. The three N-H bond dipoles do not cancel out due to the lone pair on nitrogen. Non-zero dipole moment.

2. HCl (Hydrogen chloride): Linear diatomic molecule with different atoms. The bond is polar and there is no symmetry to cancel the dipole. Non-zero dipole moment.

3. $$H_2O$$ (Water): Bent geometry (bond angle ~104.5°). The two O-H bond dipoles do not cancel due to the bent shape. Non-zero dipole moment.

4. $$BeF_2$$ (Beryllium fluoride): Linear geometry (180°). The two Be-F bond dipoles are equal and opposite, so they cancel out. Zero dipole moment.

5. $$BH_3$$ (Borane): Trigonal planar geometry (120°). The three B-H bond dipoles cancel out due to symmetry. Zero dipole moment.

6. $$CCl_4$$ (Carbon tetrachloride): Tetrahedral geometry. The four C-Cl bond dipoles cancel out due to perfect symmetry. Zero dipole moment.

Count: $$NH_3$$, HCl, and $$H_2O$$ have non-zero dipole moments.

The number of molecules with non-zero net dipole moment is 3.