According to the law of definite composition, any two samples of KCl will have _____.a. the same mass b. the same density c. slightly different...

There are two closely connected laws in chemistry, the law
of definite proportions, or Proust's law and the law of constant composition. The former
sates that all chemicals contain the same proportion of elements by mass and the latter
states that any sample of a given chemical compound will always have the same elemental
composition.

In the case of KCl, the elemental composition
is one atom of potassium (K) and one atom of chlorine (Cl). This is maintained for all
samples of KCl.

Therefore the completion of the statement
you have provided, any two samples of KCl will have _____, according to the law of
constant composition is, "the same elemental composition."