IIT JEE , AIEEE Forum - Chemistry , Physical Chemistry - how many hydrogen bonds are there in water molecule???

joy_iit

how many hydrogen bonds are there in water molecule???

rachit12

4 !
i guess !!

joy_iit

answer is true

but

how is it four ???

sriram.a

I think 3hydrogen bonds 1is intermolecular hydrogen bonding & other 2 are covalent bonds

joy_iit

answer is 4 .

but how ??

can u tell me that hydrogen bond means bond between H-H only??

learner

But, technically speaking, when you say 1 molecule,you consider it as an independent entity...so how does the intermolecular H bond count??

And the covalent bonds are also not hydrogen bonds..they're just that-covalent...

A hydrogen bond is a special type of dipole-dipole force that exists between an electronegative atom and a hydrogen atom bonded to another electronegative atom (Nitrogen, Oxygen or Fluorine). ..

source : wikipedia..

if you say how many H bonds are there between 2 H2O molecules,the answer should be 1..

someone pl clarify this..

joy_iit

ok so hydrogen bond can be between H and O
so answer is 4 .
i got it.
as there is 2 nonbonding pairs in H2O molecule ,
4 H atoms can form hydrogen bond

am i true ?

dev_22oct

there are 4 hydrogen bonds formed by water molecule ...2 r formed with 2 hydrogen and 2 with oxygen..

vsraghuvar

Hydrogen bonds in water

The most ubiquitous, and perhaps simplest, example of a hydrogen bond is found between water molecules. In a discrete water molecule, water has two hydrogen atoms and one oxygen atom. Two molecules of water can form a hydrogen bond between them; the simplest case, when only two molecules are present, is called the water dimer and is often used as a model system. When more molecules are present, as is the case in liquid water, more bonds are possible because the oxygen of one water molecule has two lone pairs of electrons, each of which can form a hydrogen bond with hydrogens on two other water molecules. This can repeat so that every water molecule is H-bonded with up to four other molecules, as shown in the figure (two through its two lone pairs, and two through its two hydrogen atoms.)

Liquid water's high boiling point is due to the high number of hydrogen bonds each molecule can have relative to its low molecular mass, not to mention the great strength of these hydrogen bonds. Realistically the water molecule has a very high boiling point, melting point and viscosity compared to other similar substances not conjoined by hydrogen bonds. The reasoning for these attributes is the inability to, or the difficulty in, breaking these bonds. Water is unique because its oxygen atom has two lone pairs and two hydrogen atoms, meaning that the total number of bonds of a water molecule is up to four. For example, hydrogen fluoride?which has three lone pairs on the F atom but only one H atom?can have a total of only two bonds (ammonia has the opposite problem: three hydrogen atoms but only one lone pair).

H-F...H-F...H-F
The exact number of hydrogen bonds in which a molecule in liquid water participates fluctuates with time and depends on the temperature. From TIP4P liquid water simulations at 25 °C, it was estimated that each water molecule participates in an average of 3.59 hydrogen bonds. At 100 °C, this number decreases to 3.24 due to the increased molecular motion and decreased density, while at 0 °C, the average number of hydrogen bonds increases to 3.69.[5] A more recent study found a much smaller number of hydrogen bonds: 2.357 at 25 °C.[6] The differences may be due to the use of a different method for defining and counting the hydrogen bonds.

Where the bond strengths are more equivalent, one might instead find the atoms of two interacting water molecules partitioned into two polyatomic ions of opposite charge, specifically hydroxide (OH?) and hydronium (H3O+). (Hydronium ions are also known as 'hydroxonium' ions.)

H-O? H3O+
Indeed, in pure water under conditions of standard temperature and pressure, this latter formulation is applicable only rarely; on average about one in every 5.5 × 108 molecules gives up a proton to another water molecule, in accordance with the value of the dissociation constant for water under such conditions. It is a crucial part of the uniqueness of water.

vsraghuvar

plz rate me ..
plzzzzz

ramkumar_november

there are four hydrogen bonds in water molecule ........

see this.....

joy_iit

in H2O there is two lone pairs means 4 electrons ,
and one H atom needs one electron to form bond,
then four H bonds are formed by lone pair of H2O.
am i true ?

rtiit

right one given by ramkumar

u can better understand it by drawing figure........

learner

Thanks!

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