– To understand the autoionization reaction of liquid water.. – To know the relationship among pH, pOH, and \(pK_w\).

For example, when a strong acid such as HCl dissolves in water, it dissociates into chloride ions (\(Cl^−\)) and protons (\(H^+\)). The proton, in turn, reacts with a water molecule to form the hydronium ion (\(H_3O^+\)):

In this reaction, \(\ce{HCl}\) is the acid, and water acts as a base by accepting an \(\ce{H^{+}}\) ion. The reaction in Equation \(\ref{16.3.1a}\) is often written in a simpler form by removing \(\ce{H2O}\) from each side:

pH is a measure of the amount of Hydrogen ions (H+) in a solution. Ions are just atoms that have an electric charge on them, so H+ is a hydrogen atom with charge of 1

The amount of H+ that is made in pure water is about equal to a pH of 7. For those who want a more complicated answer, pH is defined: pH = -log10[H+], where [H+] is the concentration of H+ , expressed in moles/liter

In solutions with other ions (say Na+ or Cl-) there’s no such constraint, so the H+ and OH- concentrations no longer equal. Thus NaOH forms a base, with lots of OH-, and HCl forms an acid, with lots of H+.

– To understand the autoionization reaction of liquid water.. – To know the relationship among pH, pOH, and \(pK_w\).

For example, when a strong acid such as HCl dissolves in water, it dissociates into chloride ions (\(Cl^−\)) and protons (\(H^+\)). The proton, in turn, reacts with a water molecule to form the hydronium ion (\(H_3O^+\)):

In this reaction, \(\ce{HCl}\) is the acid, and water acts as a base by accepting an \(\ce{H^{+}}\) ion. The reaction in Equation \(\ref{16.3.1a}\) is often written in a simpler form by removing \(\ce{H2O}\) from each side:

In the preceding section we saw examples where water can function as either an acid or a base, depending on the nature of the solute dissolved in it. In fact, in pure water or indeed any aqueous solution, water acts both as an acid and a base

This type of reaction, in which a substance ionizes when one molecule of the substance reacts with another molecule of the same substance, is referred to as .. Pure water undergoes autoionization to a very slight extent

The equilibrium constant for the ionization of water is called the:. H2O (l) + H2O (l) ⇌ H3O+ (aq) + OH– (aq) Kw = [H3O+][OH–]

– Explain the characterization of aqueous solutions as acidic, basic, or neutral. – Express hydronium and hydroxide ion concentrations on the pH and pOH scales

The concentrations of these ions in a solution are often critical determinants of the solution’s properties and the chemical behaviors of its other solutes, and specific vocabulary has been developed to describe these concentrations in relative terms. A solution is neutral if it contains equal concentrations of hydronium and hydroxide ions; acidic if it contains a greater concentration of hydronium ions than hydroxide ions; and basic if it contains a lesser concentration of hydronium ions than hydroxide ions.

One such scale that is very popular for chemical concentrations and equilibrium constants is based on the p-function, defined as shown where “X” is the quantity of interest and “log” is the base-10 logarithm:. The pH of a solution is therefore defined as shown here, where [H3O+] is the molar concentration of hydronium ion in the solution:

– Explain the characterization of aqueous solutions as acidic, basic, or neutral. – Express hydronium and hydroxide ion concentrations on the pH and pOH scales

The concentrations of these ions in a solution are often critical determinants of the solution’s properties and the chemical behaviors of its other solutes, and specific vocabulary has been developed to describe these concentrations in relative terms. A solution is neutral if it contains equal concentrations of hydronium and hydroxide ions; acidic if it contains a greater concentration of hydronium ions than hydroxide ions; and basic if it contains a lesser concentration of hydronium ions than hydroxide ions.

One such scale that is very popular for chemical concentrations and equilibrium constants is based on the p-function, defined as shown where “X” is the quantity of interest and “log” is the base-10 logarithm:. The pH of a solution is therefore defined as shown here, where [H3O+] is the molar concentration of hydronium ion in the solution:

As you learned in Chapter 4 “Reactions in Aqueous Solution” and Chapter 8 “Ionic versus Covalent Bonding”, acids and bases can be defined in several different ways (Table 16.1 “Definitions of Acids and Bases”). Recall that the Arrhenius definition of an acid is a substance that dissociates in water to produce H+ ions (protons), and an Arrhenius base is a substance that dissociates in water to produce OH− (hydroxide) ions

Although Brønsted and Lowry defined an acid similarly to Arrhenius by describing an acid as any substance that can donate a proton, the Brønsted–Lowry definition of a base is much more general than the Arrhenius definition. In Brønsted–Lowry terms, a base is any substance that can accept a proton, so a base is not limited to just a hydroxide ion

Consequently, all Brønsted–Lowry acid–base reactions actually involve two conjugate acid–base pairs and the transfer of a proton from one substance (the acid) to another (the base). In contrast, the Lewis definition of acids and bases, discussed in Chapter 8 “Ionic versus Covalent Bonding”, focuses on accepting or donating pairs of electrons rather than protons

Ionisation is defined as the process by which an atom or molecule gains or loses a positive or negative charge as a result of chemical changes. An ion is an electrically charged atom or molecule that results

The basic ionisation reaction can be represented as follows:. Ionisation can occur as a result of the loss of an electron in collisions with subatomic particles, collisions with other atoms, molecules, and ions, or interactions with electromagnetic radiation.

When a strong acid like HCl dissolves in water, it separates into chloride ions (Cl–) and protons (H+). In turn, the proton reacts with a water molecule to form the hydronium ion (H3O+):

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).. In chemistry, hydronium (hydroxonium in traditional British English) is the common name for the aqueous cation H3O+, the type of oxonium ion produced by protonation of water

In fact, acids must be surrounded by more than a single water molecule in order to ionize, yielding aqueous H+ and conjugate base. Three main structures for the aqueous proton have garnered experimental support: the Eigen cation, which is a tetrahydrate, H3O+(H2O)3, the Zundel cation, which is a symmetric dihydrate, H+(H2O)2, and the Stoyanov cation, an expanded Zundel cation, which is a hexahydrate: H+(H2O)2(H2O)4.[1][2] Spectroscopic evidence from well-defined IR spectra overwhelmingly supports the Stoyanov cation as the predominant form.[3][4][5][6] For this reason, it has been suggested that wherever possible, the symbol H+(aq) should be used instead of the hydronium ion.[2]

The concentration of hydroxide ions analogously determines a solution’s pOH. The molecules in pure water auto-dissociate into aqueous protons and hydroxide ions in the following equilibrium:

– Explain the characterization of aqueous solutions as acidic, basic, or neutral. – Express hydronium and hydroxide ion concentrations on the pH and pOH scales

The concentrations of these ions in a solution are often critical determinants of the solution’s properties and the chemical behaviors of its other solutes, and specific vocabulary has been developed to describe these concentrations in relative terms. A solution is neutral if it contains equal concentrations of hydronium and hydroxide ions; acidic if it contains a greater concentration of hydronium ions than hydroxide ions; and basic if it contains a lesser concentration of hydronium ions than hydroxide ions.

One such scale that is very popular for chemical concentrations and equilibrium constants is based on the p-function, defined as shown where “X” is the quantity of interest and “log” is the base-10 logarithm:. The pH of a solution is therefore defined as shown here, where [H3O+] is the molar concentration of hydronium ion in the solution:

We are surrounded by dilute solutions of acids and bases, inside and out. The orange juice and coffee that help us start our day are acidic, and the gastric juices they mix with in our stomach are also naturally acidic

Now that you know about reversible reactions and how solutions are described in terms of molarity, you will be able to understand the origin of the pH scale for describing acids and what the pH value says about an acidic or basic solution.. According to the Arrhenius theory of acids and bases, when an acid is added to water, it donates an H+ ion to water to form H3O+ (often represented by H+)

An Arrhenius base is a substance that generates hydroxide ions, OH-, in water. The higher the concentration of OH- in a solution, the more basic the solution is.