All the elements in one group have the same number of valence electrons.
<span>The
bent geometry of the water molecule gives a slight overall negative
charge to the oxygen side of the molecule and a slight overall positive
charge to the hydrogen side of the molecule. This slight separation of
charges gives the entire molecule an electrical polarity, so water
molecules are dipolar.</span>
Free expansion refers to uninhibited or provoked expansion, i.e. it’s expanding on its own, by itself. The only situation in which this occurs is B, as the gas is allowed to expand by itself. A involves a reaction that forces the expansion, C involves the gas performing work, and D involves thermal expansion.
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