Total Hydrogen Bonds in Liquid Water

Estimate the total number of hydrogen bonds in a volume of liquid water, dividing by two because each bond is shared between two molecules to avoid double-counting.

$$N_{HB}=\frac{N\times b}{2}$$

Variables

Symbol	Meaning	Unit
$N_{HB}$	Total number of hydrogen bonds	bonds
N	Number of water molecules	molecules
b	Average hydrogen bonds per molecule (about 3.4 at room temperature, approaching 4 near freezing)	bonds/molecule

Worked example

With N = 7.91 x 10^24 molecules and b = 3.4 bonds per molecule: N_HB = (7.91 x 10^24 x 3.4) / 2 = 1.34 x 10^25 hydrogen bonds.

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Part of The Blueprint of Water