Number of compounds from the following with zero dipole moment is ______ $$HF, H_2, H_2S, CO_2, NH_3, BF_3, CH_4, CHCl_3, SiF_4, H_2O, BeF_2$$

We need to count the number of compounds with zero dipole moment from the given list.

Key concept: A molecule has zero dipole moment if it is either nonpolar (same atoms bonded) or if its geometry causes the individual bond dipoles to cancel out due to symmetry.

Let us check each compound:

1. HF — Linear, polar bond. Dipole moment $$\neq 0$$.

2. $$H_2$$ — Homonuclear diatomic, nonpolar. Dipole moment = 0.

3. $$H_2S$$ — Bent shape (like water). Dipole moment $$\neq 0$$.

4. $$CO_2$$ — Linear, $$O=C=O$$. Bond dipoles cancel. Dipole moment = 0.

5. $$NH_3$$ — Trigonal pyramidal with lone pair. Dipole moment $$\neq 0$$.

6. $$BF_3$$ — Trigonal planar, symmetric. Bond dipoles cancel. Dipole moment = 0.

7. $$CH_4$$ — Tetrahedral, symmetric. Bond dipoles cancel. Dipole moment = 0.

8. $$CHCl_3$$ — Tetrahedral but asymmetric (one H, three Cl). Dipole moment $$\neq 0$$.

9. $$SiF_4$$ — Tetrahedral, symmetric. Bond dipoles cancel. Dipole moment = 0.

10. $$H_2O$$ — Bent shape. Dipole moment $$\neq 0$$.

11. $$BeF_2$$ — Linear, $$F-Be-F$$. Bond dipoles cancel. Dipole moment = 0.

Compounds with zero dipole moment: $$H_2$$, $$CO_2$$, $$BF_3$$, $$CH_4$$, $$SiF_4$$, $$BeF_2$$ = 6 compounds.

The answer is 6.