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In chemistry and biochemistry, the Henderson–Hasselbalch equation = + ([] []) relates the pH of a chemical solution of a weak acid to the numerical value of the acid dissociation constant, K a, of acid and the ratio of the concentrations, [] [] of the acid and its conjugate base in an equilibrium.
With pOH obtained from the pOH formula given above, the pH of the base can then be calculated from =, where pK w = 14.00. A weak base persists in chemical equilibrium in much the same way as a weak acid does, with a base dissociation constant (K b) indicating the strength of the base. For example, when ammonia is put in water, the following ...
The formula for this acid is generally written H 3 PO 2, but a more descriptive presentation is HOP(O)H 2, which highlights its monoprotic character. Salts derived from this acid are called hypophosphites. [3] HOP(O)H 2 exists in equilibrium with the minor tautomer HP(OH) 2. Sometimes the minor tautomer is called hypophosphorous acid and the ...
Relation between pH and pOH. Red represents the acidic region. Blue represents the basic region. pOH is sometimes used as a measure of the concentration of hydroxide ions, OH −. By definition, pOH is the negative logarithm (to the base 10) of the hydroxide ion concentration (mol/L). pOH values can be derived from pH measurements and vice-versa.
Pauling's second rule is that the value of the first pK a for acids of the formula XO m (OH) n depends primarily on the number of oxo groups m, and is approximately independent of the number of hydroxy groups n, and also of the central atom X. Approximate values of pK a are 8 for m = 0, 2 for m = 1, −3 for m = 2 and < −10 for m = 3. [28]
Hypophosphoric acid can be prepared by the reaction of red phosphorus with sodium chlorite at room temperature. [2]2 P + 2 NaClO 2 + 2 H 2 O → Na 2 H 2 P 2 O 6 + 2 HCl. A mixture of hypophosphoric acid, phosphorous acid (H 3 PO 3) and phosphoric acid (H 3 PO 4) is produced when white phosphorus oxidises in air when partially immersed in water.
Phosphinous acids are usually organophosphorus compounds with the formula R 2 POH. They are pyramidal in structure. Phosphorus is in the oxidation state III. Most phosphinous acids rapidly convert to the corresponding phosphine oxide, which are tetrahedral and are assigned oxidation state V.
The ratio of concentration of conjugate acid/base to concentration of the acidic/basic indicator determines the pH (or pOH) of the solution and connects the color to the pH (or pOH) value. For pH indicators that are weak electrolytes, the Henderson–Hasselbalch equation can be written as: