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When an acid is dissolved in water C A = C H = C a, the concentration of the acid, so [A] = [H]. After some further algebraic manipulation an equation in the hydrogen ion concentration may be obtained. [] + [] =
C A is the analytical concentration of the acid and C H is the concentration the hydrogen ion that has been added to the solution. The self-dissociation of water is ignored. A quantity in square brackets, [X], represents the concentration of the chemical substance X. It is understood that the symbol H + stands for the hydrated hydronium ion.
The Henderson–Hasselbalch equation assumes that the autoionization of water is negligible and that the dissociation or hydrolysis of the acid and the base in solution are negligible (in other words, that the formal concentration is the same as the equilibrium concentration). For an acid-base equilibrium such as HA ⇌ H + + A −, the Charlot ...
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.
The concentration of hydrogen ions and pH are inversely proportional; in an aqueous solution, an increased concentration of hydrogen ions yields a low pH, and subsequently, an acidic product. By definition, an acid is an ion or molecule that can donate a proton, and when introduced to a solution it will react with water molecules (H 2 O) to ...
When reacting with a stronger acid, water acts as a base; when reacting with a stronger base, it acts as an acid. [88] For instance, water receives an H + ion from HCl when hydrochloric acid is formed: + ⇌ H 3 O + + Cl −. In the reaction with ammonia, NH 3, water donates a H + ion, and is thus acting as an acid: + ⇌ NH +
Cation exchange is widely used to remove ions such as Na + and Ca 2+ from aqueous solutions, producing demineralized water. The acid is used to rinse the cations from the resins. [25] Na + is replaced with H + and Ca 2+ with 2 H +. Ion exchangers and demineralized water are used in all chemical industries, drinking water production, and many ...
Unlike H + (aq) in neutral solutions that result from water's autodissociation, in acidic solutions, H + (aq) is long-lasting and concentrated, in proportion to the strength of the dissolved acid. pH was originally conceived to be a measure of the hydrogen ion concentration of aqueous solution. [17]