Ask A Scientist Chemistry Archive

name         Donna S.
status       educator
age          40s

Question -   Can you tell me please Since hydrogen peroxide is a non
symmetric molecule what is its polarity? ( I think that it must be
neutral) Thanks
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The polarity of H2O2 vs. H2O and N2H2(hydrazine) vs. NH3 is measured by
comparing the dipole moments. The dipole moment of H2O2 and water is 2.2 and
1.85 respectively. The dipole moment of N2H2 and NH3 is 1.75 vs. 1.47 debye
units (cgs. system). This is surprising at first glance since one might be
tempted to assign a trans - planar structure to H2O2 and N2H2. This
temptation in incorrect however. The higher polarity indicates that the
actual structure of these molecules is a skewed cis - structure with the
hydrogen atoms pointing in the same direction and the lone pairs oriented in
the same but opposite direction with respect to the O--O and the N--N bonds.
Only this configuration would result in dipole moments larger for these
molecules compared to H2O and NH3.

Vince Calder
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