@秦山事花 省级精品课程申报 S=Kp(SrS04)/c(S042)=7.6×10'/0.10=7.6×10(mol·L) (③)计算表明，SSO4的溶解度比在纯水中的溶解度要小100多倍。这是因为在SS04的沉淀 平衡系统中，若加入含有共同离子SO,的试剂后，会有更多的SrSO沉淀生成，致使SrS0溶 解度降低。这就是难溶电解质沉淀溶解平衡的同离子效应的影响所致。 21.The fluoride ions in drinking water the convert hydroxyapatite,Ca(PO4)OH,of teeth into fluorapatite,Cas(PO)3E.The Ksp of the two compounds are 1.0x1036 and 1.0x10, respectively.What are the molar solubilities of each substance?The solubility equilibria to consider are: Cas(PO4)OH(s) -5Ca2(aq)+3PO(aq)+OH(aq) Cas(POA)aF(s) =5Ca2*(aq)+3P0,(aq)+F(aq) 解：设Cas(PO43OH,和Ca(POF的溶解度分别为S1和S, (1)Cas(PO4)3OH(s) -5Ca2(aq)+3PO(aq)+OH(aq) S Kp(Ca:(PO4:OH)=ICa2TIPOTIOH]=(5S3S'(S) =55×33XS,9=84375S9=1.0×1036 S1=2.8×105 (2)Ca:(PO4):F(s) -5Ca2(aq)+3PO(aq)+F(aq) Kp(Ca3(P0F)=Ca2TIP0,IF1=(5S23S,S)=55×33×S,9 =843755S,°=1.0X1060 S2=6.1×108 22.(1)A solution is 0.15 mol-L in Pb2*and 0.20 molL in Ag'.If solid NazSO is very slowly added to this solution,which will precipitate first,PbSO or AgSO? (2)The addition of NazSO is continued until the second cation just starts to precipitate as the sulfate.What is the concentration of the first eation at this point?Kp for PbSO=1.3x10 Ag2S04=1.2×10 解：(1)PbSO:开始沉淀时所需的SO:2最低浓度： c(S02=Kp(PbS0)/c(Pb2=1.3×10/0.15=8.67×108(mol·L Ag2S04开始沉淀时所需的S042最低浓度： 7