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The hydroxide ion is naturally produced from water by the self-ionization reaction: [2] H 3 O + + OH − ⇌ 2H 2 O. The equilibrium constant for this reaction, defined as K w = [H +][OH −] [note 1] has a value close to 10 −14 at 25 °C, so the concentration of hydroxide ions in pure water is close to 10 −7 mol∙dm −3, to
The ability for ions to move freely through the solvent is a characteristic of an aqueous strong electrolyte solution. The solutes in a weak electrolyte solution are present as ions, but only in a small amount. [3] Nonelectrolytes are substances that dissolve in water yet maintain their molecular integrity (do not dissociate into ions).
Water is also central to acid-base neutrality and enzyme function. An acid, a hydrogen ion (H +, that is, a proton) donor, can be neutralized by a base, a proton acceptor such as a hydroxide ion (OH −) to form water. Water is considered to be neutral, with a pH (the negative log of the hydrogen ion concentration) of 7 in an ideal state.
Both the negatively charged anion HO −, called hydroxide, and the neutral radical HO·, known as the hydroxyl radical, consist of an unbonded hydroxy group. According to IUPAC definitions, the term hydroxyl refers to the hydroxyl radical (·OH) only, while the functional group −OH is called a hydroxy group. [1]
They consist of hydroxide (OH −) anions and metallic cations, [1] and are often strong bases. Some metal hydroxides, such as alkali metal hydroxides, ionize completely when dissolved . Certain metal hydroxides are weak electrolytes and dissolve only partially in aqueous solution .
This includes ions which form sulfides that are insoluble at high concentrations. The reagents used are H 2 S in the presence of NH 4 OH. NH 4 OH is used to increase the concentration of the sulfide ion, by the common ion effect - hydroxide ions from NH 4 OH combine with H + ions from H 2 S, which shifts the equilibrium in favor of the ionized ...
In 1884, Svante Arrhenius proposed that a base is a substance which dissociates in aqueous solution to form hydroxide ions OH −. These ions can react with hydrogen ions (H + according to Arrhenius) from the dissociation of acids to form water in an acid–base reaction. A base was therefore a metal hydroxide such as NaOH or Ca(OH) 2.
The solubility increases down the column as the alkali metal ions become larger and the lattice enthalpies decrease. [1] All alkali metal hydroxides are strong bases, meaning that they dissociate completely in solution to give OH − ions. As strong bases, alkali hydroxides are highly corrosive and are used in cleaning products.