Chemistry, asked by rakhshandirect3951, 10 months ago

From the value of ionic product of water at 25 degree Celsius , find the concentration of hydroxylions .

Answers

Answered by laxmigupta19lg9

Answer:

Water dissociation (autoionization; self-ionization) occurs endothermically d due to electric field fluctuations between neighboring molecules. Dipole librations [191], resulting from thermal effects and favorable localized hydrogen bonding, [567] together with nuclear quantum effects [2025], cause these fluctuations. The process may be facilitated by exciting the O-H stretch overtone vibration [393]. Once formed (at an average concentration of about 1 M H2O-H+···OH- [1984]),h the ions may separate by means of the Grotthuss mechanism but normally (>99.9%) rapidly recombine (≈ 20 ps [2171]) with a frequency in the terahertz range. Rarely (about once every eleven hours per molecule at 25 °C, or less than once a week at 0 °C), the localized hydrogen bonding arrangement breaks before allowing the separated ions to return [191]. The pair of ions (H+, OH-)g hydrate independently and continue their separate existence afor about 70 μs (this lifetime also dependent on the extent of hydrogen-bonding, being shorter at lower temperatures). They tend to recombine when separated by only one or two water molecules.

H2O H+ + OH-

Kw = [H+] ˣ [OH-]

Kw is a dimensionless number as the included concentrations are relative to the standard states (e.g., 1 mol ˣ L-1). This low occurrence of the ions means that at neutrality (pH 7 at 25 °C) c, similarly charged ions are, on average, separated by vast distances (≈ 0.255 μm) in molecular terms and (for example) bacteria contain only a few tens of free hydrogen ions (~ 30 in an Escherichia coli). Contributing to this effect are the high dielectric constant (encouraging charge separation) and high concentration of H2O (≈ 55.5 M; increasing the absolute amount dissociated). The mean lifetime of a hydroxonium ion (1 ps; about the same as that of a hydrogen bond) is such that the charge could be associated with over 107 molecules of water before neutralization.

Although the extent of dissociation is tiny ([H+]/[H2O] = 2.8 ˣ 10-9 at 37 °C), the dissociation and consequential changes in the tiny concentrations of hydrogen ions have absolute importance to living processes. Hydrogen and hydroxyl ions are produced already hydrated.

H2O (liq) H+(aq) + OH- (aq)

where the subscripts 'liq' and ‘aq’ indicate that the species are in or within the aqueous liquid phase. l

Hydration enthalpies of protons and hydroxides, from [1938b]

The protons (H+, hydrons) initially hydrate as hydroxonium ions, H3O+(also called oxonium or hydronium ions) and do not exist as naked protons in liquid or solid water, where they interact extremely strongly with electron clouds. All three hydrogen atoms in the hydroxonium ion are held by strong covalent bonds and are equivalent (that is, C3vsymmetry in a vacuum). The thermodynamic properties of the dissociation at 25 °C and 0.1 MPa are ΔU° = 59.5 kJ ˣ mol-1, ΔV° = 22.13 cm3 ˣ mol-1, ΔH° = 55.8 kJ ˣ mol-1, ΔG° = 79.9 kJ ˣ mol-1, ΔS° = -80.8 J ˣ K-1 ˣ mol-1 [1938]. The proton is never found unhydrated in aqueous solution and the hydroxonium ions, H3O+, also has negligible independent existence in an aqueous environment [2134]. All the hydroxonium ion protons are predominantly hydrogen-bonded causing further hydration to H3O+(H2O)n, where n depends on the conditions such as temperature, solutes, pressure and method of determination. [H+] is often written instead of [H3O+].

To avoid the misleading presumption of the existence of bare protons similar to other bare cations (but see [2132] for an alternative view), the above equations are better written as:

2 H2O(aq) H3O+(aq) + OH-(aq)

Kw = [H3O+] ˣ [OH-]

Explanation:

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Answered by CarlynBronk

The question is incomplete, here is the complete question:

From the value of ionic product of water is 25°C, find out the concentration of hydroxyl ion (at 25°C concentration of hydrogen ions in water is 10⁻⁷ M)