化学PH（Chemical PH）.doc

化学PH（Chemical PH） 1. The pH value of the solution PH = 1. The definition of pH: - lg [H +] note: (1) at 25 ℃ : pH + POH = = 14 (2) the pH of the scope of application: CH + (10-14, 1), namely pH range of temperature is (0, 14) note: any [H +] indicates zero in aqueous solution, but pH value is 0, the [H +] = 1 mol/L, general [H +] 1 mol/L, the pH 0, thus directly with [H +] said. 2. The determination of pH: pH test paper, pH meter. PH paper: (1) can only read integer (2) the method of use: apply with a glass rod under test liquid in the centre of pH test paper, than with the standard color swatches for color immediately, to half a minute for the color change of the standards. (3) the pH paper in advance cant wetting 3. PH calculation: key: (1) consider of reaction (ignoring volume change) there are three possible: - (1) if the acid and alkali neutralization. Namely, nH + = nOH, pH = 7. (2) if the excess acid, and the excessive [H +], and seeking pH. - (3) if the excessive alkali, and the excess [OH], and after pOH for pH. (2) to a single acid solution: looking for CH + pH; For a single alkali solution: first find hydroxyl ions concentration to hydrogen ion concentration and then converted to PH 4. The acid solution was alkaline judgment problem: - (1) the absolute standard: depends on the solution of [H +], [OH] relative size. (2) at 25 ℃ : on the basis of pH = = 7. The hydrolysis of salt: 1. Hydrolysis rule: there is the salt to hydrolyze, the weak hydrolysis, the weaker the hydrolysis, the dihydrolysis of the dihydrolysis, who is strong, the other is neutral, the double weak is specific. (it depends on the relative strength of the weak base of the weak acid) (such as NH4CN alkaline CH3COONH4 neutral (NH4) 2SO3 acidity 2. Note: (1) salt hydrolysis for neutralization reaction of adverse reaction, but the degree is small, generally not more than 10 ℅. And its endothermic. (2) the hydrolysis of salt does not necessarily affect the PH of the solution, such as CH3COONH