Which bond pair does not have a polar covalent bond?
a. p – cl
b. o – h
c. s – cl
d. h – cl
e. cl – cl

The answer is E. Cl -- Cl

Chloride, Cl2, has a non-polar covalent bond because both molecules making up the compound are identical. This results to a diatomic molecule, which are known non-polar molecules. Since both sides of the bond are also the same, there is equal sharing of electrons. Polar covalent bonds are those that have unequal sharing of electrons.

D)can be increased in a closed system

They are all decomposition reactions.