CHEM（急！２０分）

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2007-02-13 18:18:11 補充：
first use acidified AgNO3 (acidified with HNO3), MgCl2 will form a white ppt.Ag+ + Cl- ==> AgCl(s)for the remaining two, add excess NaOH. both form ppt but that of Zn will redissolve in excess NaOH

2007-02-13 18:18:20 補充：
Mg2+ + 2OH- ==> Mg(OH)2(s) <== will not redissolveZn2+ + 2OH- ==> Zn(OH)2 <== will redissolve by the equation:Zn(OH)2 + 2OH- ==> [Zn(OH)4]2- (aq)

2007-02-13 18:18:37 補充：
+AgCl3,MgCl2 白色沉澱Mg(NO3)2 固體有耀眼白光

2007-02-13 18:18:56 補充：
Firstly, the chemicals are dissolved in water. Then, acidifed silver nitrate solution into three unkown solution. The one with a precipitate formed is magnesium chloride.The precipitate is insolube AgCl.MgCl2+ 2AgNO3----->2AgCl+ Mg(NO3)2

2007-02-13 18:19:05 補充：
Secondly,excess NaOH is added to the two solution. The one with the precipitate redissoved is ZnNO3.Since Zn ions will redissolve in excess NaOH due to the formation of soluble complex salt while Mg does not. Therefore, it is ZnNO3.Zn(OH2+ 2OH- ------>Zn(OH)4 2-

Firstly, the chemicals are dissolved in water. Then, acidifed silver nitrate solution into three unkown solution. The one with a precipitate formed is magnesium chloride.The precipitate is insolube AgCl.
MgCl2+ 2AgNO3----->2AgCl+ Mg(NO3)2

Secondly,excess NaOH is added to the two solution. The one with the precipitate redissoved is ZnNO3.Since Zn ions will redissolve in excess NaOH due to the formation of soluble complex salt while Mg does not. Therefore, it is ZnNO3.
Zn(OH2+ 2OH- ------>Zn(OH)4 2-

+AgCl3,MgCl2 白色沉澱

Mg(NO3)2 固體有耀眼白光

first use acidified AgNO3 (acidified with HNO3), MgCl2 will form a white ppt.

Ag+ + Cl- ==> AgCl(s)

for the remaining two, add excess NaOH. both form ppt but that of Zn will redissolve in excess NaOH

Mg2+ + 2OH- ==> Mg(OH)2(s) <== will not redissolve
Zn2+ + 2OH- ==> Zn(OH)2 <== will redissolve by the equation:

Zn(OH)2 + 2OH- ==> [Zn(OH)4]2- (aq)