6.1 相数，组分数，自由度数 6.1.1 概念第六章第六章 相平衡相平衡 (1) 相数 P (3) 独立组分数 C(2) 物种数 SC S - R - RR: 独立化学平衡数 R: 浓度限制条件 chemical stoichiometric number electroneutrality conditionsCaCO3 (s) = CaO(s)+CO2(g)平衡 0 BB ，2NH3(g) N2 (g) 3H2 (g) n H2(g) 3n N2 (g) x H2(g) 3x N2 (g) NaCl 水溶液，Na+, Cl-, H+, OH-c(Na+) + c(H+) = c(Cl-) + c(OH-)6.1.2 相律f = C -P + 2(4) 自由度数 f为确定系统的状态，我们定义平衡系统的独立可变的 变量的数目 6.2 单组分相图 f CP2 = 1P23Pf 0，P1， 3P1P1，f2，P2，f1，P3，f0，6.2.1 H2O的相图 6.2.2 CO2 的相图 t/P/MPaO BA C0.518-56.5SolidGasLiquidCO26.3 气液相图 f CP2 = 2P24Pf 0，P1， 4P1P1，f3，P2，f2，P3，f1，P4，f0，T 固定， p-x相图 p 固定, T（沸点）-x相图 6.3.1 p-x相图 理想溶液(a) 蒸气组成pAyAp pByBpBenzene(A)- toluene(B)system (79.7 )xByBp/ 102kPa 000.3846 0.11610.25300.4553 0.22710.42950.5225 0.33830.56670.5225 0.45320.66560.66499 0.54510.75740.7166 0.63440.81790.7722 0.73270.87820.8331 0.82430.92400.8907 0.91890.96720.9179 0.95650.98270.9845 1.0001.0000.9982(b) 相图说明(c) 杠杆规则The lever rule is so called because a similar rule relates the masses at two ends of a lever to their distances from a pivot. nl = n l6.4 T-x相图 Benzene(A)- toluene(B)system (p=101.325Pa)t/CxByB 110.6200 108.750.0420.089 104.870.1320.257 103.000.1830.384 101.520.2190.395 97.760.3250.530 95.010.4670.619 92.790.4830.688 90.760.5510.742 88.630.6280.800 86.410.7120.853 84.100.8100.911 81.990.9000.958 80.101.0001.000理想溶液的T-x相图是以A的挥发度较大 (a) 混合物的分馏The number of theoretical plates is the number of steps needed to bring about a specified degree of separation of two components in a mixture. The two systems shown correspond to (a) 3, (b) 5 theoretical plates. (b) AzeotropesA high-boiling azeotrope. When the liquid of composition a is distilled, the composition of the remaining liquid changes towards b but no further. A low-boiling azeotrope. When the mixture at a is fractionally distilled, the vapour in equilibrium in the fractionating column moves towards b and then remains unchanged.The temperature-composition diagram of H2O(A) - C2H5OH(B)0.00.20.40.60.81.0 H2O(A)C2H5OH(B)xByBt/ 12010060800.00.20.40.60.81.0p=101325PaxB=0.897yB=0.89778.15The isopleth through e corresponds to the eutectic composition, the mixture with lowest melting point. 6.6 液固相图6.6.1 Eutectics 热分析法，步冷曲线CED: s(A)+ s(B)+lE(A+B)t*A Et*B E液相线t*A Ct*B D固相线E: 共熔点(b)反应体系 congruent melting incongruent melting6.6.2 Ultrapurity and controlled impurity Zone refining Partially miscibleCED s(A+B)+ s(A+B)+lE(A+B)