ACIDS, BASES, SALTS, AND pHDOE-HDBK-1015/1-93Fundamentals of ChemistryCH-01Rev. 0Page 48SaltsWhen an acid reacts with a base, two products are formed; water and a salt. A salt is an ioniccompound composed of positive ions and negative ions. The ionic bond is what keeps salts intheir molecular form. Some compounds look like salts, but are actually covalent compounds(have a covalent bond).Example:This type of acid-base reaction is called neutralization.Certain soluble salts (principally sodium, potassium, magnesium, and calcium) that have theproperty of combining with acids to form neutral salts are called alkalies. Two of the commonsalts are sodium chloride (table salt) and calcium chloride (salt put on the road in winter).Unlike acids and bases, salts vary greatly in all their properties except their ionic characteristics.Salts may taste salty, sour, bitter, astringent, sweet, or tasteless. Solutions of salts may beacidic, basic, or neutral to acid-base indicators. Fused salts and aqueous solutions of saltsconduct an electric current. The reactions of salts are numerous and varied.pHMany compounds dissolve in water and alter the hydrogen ion concentration. Compounds thatproduce hydrogen ions directly when dissolved in water are called acids, and those that producehydroxyl ions directly when dissolved in water are called bases. To treat these aspects ofchemistry more precisely, a quantitative system of expressing acidity or basicity (alkalinity) isneeded. This need could be met by using the value of [H ], where [H ] is expressed in+ +moles/liter, as a measure of acidity. But, in most cases [H ] is in the range of 10 to+ -110 moles/liter. Because numbers of this magnitude are inconvenient to work with, an-14alternate system for expressing the acidity of dilute solutions has been devised. This system isbased on a quantity called pH. ph is defined as the negative logarithm of the hydrogenconcentration, represented as [H ] in moles/liter.+pH= -log [H ](1-1)+[H ] = 10(1-2)+ -pHThe negative logarithm is specified because the logarithm of any number less than 1 is negative;thus multiplication by -1 causes the values of pH to be positive over the range in which we areinterested. (The term pH was first defined by a Danish chemist and is derived from p for theDanish word potenz (power) and H for hydrogen.)
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