Water bond angle

As the ammonia molecule possesses the same electron configuration as water (isoster-ism) and similar bond angles (water vapor bond angle 105 °, dipole moment 1.84 D), ammonia and water behave similarly in many reactions. Ammonia and water are diamagnetic. The dielectric constant of liquid ammonia is about 15 and greater than those of the most condensed gases therefore, liquid ammonia has a considerable ability to dissolve many substances. The ammonia molecule, with its free electron pair, can combine with a proton. 

As given, the bond angle is ambiguous because you cannot have an angle between only two atoms. Therefore, there must be a third atom involved in the last entry. In the case of water, it can only be H—O—H. Make it clear in your report what the third atom is, that is, give a bond angle for C—C—H and one for C=C—H, which will not be the same. 

The H—O—H angle m water (105°) and the H—N—H angles m ammonia (107°) are slightly smaller than the tetrahedral angle These bond angle contractions are easily accommodated by VSEPR by reasoning that electron pairs m bonds take up less space than an unshared pair The electron pair m a covalent bond feels the attractive force of... 

Use Learning By Modeling to make models of water methanol dimethyl ether and di tert butyl ether Mini mize their geometries and examine what happens to the C—O—C bond angle Compare the C—O bond dis tances in dimethyl ether and di tert butyl ether... 

In each case the left-hand atom of the pair as written is the least electronegative. Since dipole moments have direction as well as magnitude it is necessary to add the moments of each bond vertically. For this reason the individual dipole moments cancel each other out in carbon tetrachloride but only partially in chloroform. In other molecules, such as that of water, it is necessary to know the bond angle to calculate the dipole moment. Alternatively since the dipole moment of the molecule is measurable the method may be used to compute the bond angle. 

Water is a volatile, mobile liquid with many curious properties, most of which can be ascribed to extensive H bonding (p. 52). In the gas phase the H2O molecule has a bond angle of 104.5° (close to tetrahedral) and an interatomic distance of 95.7 pm. The dipole moment is 1.84 D. Some properties of liquid water are summarized in Table 14.8 together with those of heavy water... 

One after the other, examine methanol dimer and acetic acid dimer. Do the hydrogen-bond lengths in these systems differ significantly from the optimum distance in water dimer Are the hydrogen-bond angles in these compounds significantly different from those in water dimer Rationalize your results. 

Why is the bond angle in water smaller than tetrahedral ... 

Alcohols and phenols have nearly the same geometry around the oxygen atom as water. The R-O—H bond angle has an approximately tetrahedral value (109° in methanol, for example), and the oxygen atom is sp3-hybridized. 

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