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The pH range is commonly given as zero to 14, but a pH value can be less than 0 for very concentrated strong acids or greater than 14 for very concentrated strong bases. [2] The pH scale is traceable to a set of standard solutions whose pH is established by international agreement. [3]
The pH scale is by far the most commonly used acidity function, and is ideal for dilute aqueous solutions. Other acidity functions have been proposed for different environments, most notably the Hammett acidity function, H 0, [3] for superacid media and its modified version H − for superbasic media.
In and of themselves, pH indicators are usually weak acids or weak bases. The general reaction scheme of acidic pH indicators in aqueous solutions can be formulated as: HInd (aq) + H 2 O (l) ⇌ H 3 O + (aq) + Ind − (aq) where, "HInd" is the acidic form and "Ind −" is the conjugate base of the indicator. Vice versa for basic pH indicators ...
A pH meter is a scientific instrument that measures the hydrogen-ion activity in water-based solutions, ... (approximately 0.06 volts per pH unit) with the pH scale.
o can be mistaken as an a which could read "a.u.", meaning both ears oz ounce p. perstetur: continue part. æq. partes æquales: equal parts per: per: by or through p.c. post cibum: after meals p.c.h.s., pc&hs post cibum et hora somni: after meals and at bedtime Ph.Br., BP Pharmacopoeia Britannica: British Pharmacopoeia Ph.Eur. Pharmacopoeia ...
It is often absorbed onto filter paper to produce one of the oldest forms of pH indicator, used to test materials for acidity. In an acidic medium, blue litmus paper turns red, while in a basic or alkaline medium, red litmus paper turns blue. In short, it is a dye and indicator which is used to place substances on a pH scale.
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Conversely, when pH = pK a, the concentration of HA is equal to the concentration of A −. The buffer region extends over the approximate range pK a ± 2. Buffering is weak outside the range pK a ± 1. At pH ≤ pK a − 2 the substance is said to be fully protonated and at pH ≥ pK a + 2 it is fully dissociated (deprotonated).