Pick out the molecule which has zero dipole moment.

Elements $X, Y$ and $Z$ have $4, 5$ and $7$ valence electrons respectively.
$(a)$ Write the molecular formula of the compounds formed by these elements individually with hydrogen.
$(b)$ Which of these compounds will have the highest dipole moment?

Which compound among the following will have a permanent dipole moment?

The correct order of dipole moment for the following molecules is:

$Cis$-but$-2$-ene is polar and $trans$-but$-2$-ene is non-polar. Explain.

Which of the following bonds is the most polar?