The activity of components of solution is the concentration of components calculated taking into account their interaction in solution. The term "activity" was offered in 1907 by the American scientist Lewis as the size which use rather just will help to describe properties of real solutions.
Instruction
1. There are various experimental methods of determination of activity of components of solution. For example, on temperature increase of boiling of the studied solution. If this temperature (designate it by a symbol T) higher, than temperature of boiling of pure solvent, a natural logarithm of activity of solvent is calculated on the following formula: lnA = (-∆H/RT0T) x ∆T. Where, n – warmth of evaporation of solvent in a temperature interval between That and T.
2. You can determine activity of components of solution by fall of temperature of freezing of the studied solution. In this case, the natural logarithm of activity of solvent is calculated by the following formula: lnA = (-∆H/RT0T) x ∆T, where, ∆H – warmth of freezing of solution in an interval between temperature of freezing of solution (T) and temperature of freezing of pure solvent (That).
3. Calculate activity by means of a method of studying balance of chemical reaction with a gas phase. Let's assume, at you there takes place chemical reaction between fusion of oxide of some metal (designate it by the general formula of MeO) and gas. For example: MeO + H2 = + H2O - that is oxide of metal is restored by Me to pure metal, with formation of water in the form of water vapor.
4. In this case the constant of balance of reaction pays off as follows: Kr = (pH2O x to Ama) / (rn2 x Ameo) where p is the partial vapor pressure of hydrogen and water respectively, And – activities of pure metal and its oxide respectively.
5. Calculate activity by method of calculation of electromotive force of the galvanic cell formed by solution or fusion of electrolyte. This way is considered one of the most exact and reliable for determination of activity.