Chemical Bonding and Molecular Structure: Chemistry | JEE Main
In an ice crystal, each water molecule is hydrogen bonded to ……………neighbouring molecules.
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Hint 1 of 2
How many hydrogen-bond donors (H atoms) and acceptors (lone pairs on oxygen) does a single H2O molecule possess?
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Correct answer
In an ice crystal, each water molecule forms four hydrogen bonds with four neighbouring molecules in a tetrahedral arrangement.
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Solution
StepWorking
01given
Crystal structure of ice (ordinary hexagonal ice Ih).
02find
The number of neighbouring water molecules to which each H2O molecule is hydrogen bonded in ice.
03visualise
In ice, each oxygen atom is sp3 hybridized with two covalent O-H bonds and two lone pairs. Each hydrogen atom forms an H-bond with a lone pair of an adjacent molecule (2 H-bonds donated). Each lone pair accepts an H-bond from an adjacent molecule (2 H-bonds accepted). This gives a tetrahedral coordination environment.
04strategise
Total number of hydrogen bonds per molecule = (H-bonds donated)+(H-bonds accepted)=2+2=4. Therefore, each water molecule is connected to 4 neighbours.
05execute
Total neighbouring bonded molecules = 2+2=4.
✓verify
This 4-coordination creates an open tetrahedral framework that explains why ice has a lower density than liquid water at 0 °C.
Hints that build this answer step by step
How many hydrogen-bond donors (H atoms) and acceptors (lone pairs on oxygen) does a single H2O molecule possess?
2 donors and 2 acceptors
Given that each water molecule donates 2 hydrogen bonds and accepts 2 hydrogen bonds in the ice lattice, what is the total number of neighbouring water molecules it is bonded to?
Why are there 4 hydrogen bonds if water only has 2 hydrogen atoms?
Each water molecule donates 2 hydrogen bonds via its 2 H atoms. It also accepts 2 hydrogen bonds via the 2 lone pairs on the O atom. This makes a total of 4 hydrogen bonds to 4 distinct neighbouring molecules.