更新1:
我想知點解test3唔可以係ag+,test3係話有白色ppt出現
acid and base!
2011-03-29 4:31 am
the following table lists the results of four tests carried out on a solid mixture of two salts.test3:dissolve the mixture in water.add dilute hcl the bacl2 solution.result: a white precipitate formedtest4:dissolve the mixture in h2o.add dil.hno3 the agno3 solutionresult:a yellow precipitate formedidentify the ions present in the sample of two mixed salts from test3 and test4
回答 (1)
2011-03-29 9:16 pm
✔ 最佳答案
3. sulphate ion is present.
barium ion reacts with sulphate to give permanent white precipitate:
Ba(2+) + SO4(2-) ------> BaSO4
hydrochloric acid is added to dissolve any other possible interfering anions, such as sulphite and carbonate:
SO3(2-) + 2H(+) -----> H2SO3 ------> H2O + SO2
4.
iodide is present, giving yellow precipitate.
Ag(+) + I(-) ------> AgI
(silver bromide is pale yellow (creamy) ppt., chloride is white)
dil. nitric acid is added to dissolve any interfering ions, such as carbonate, and oxide (hydroxide):
2Ag(+) + 2OH(-) ------> Ag2O + H2O
Ag2O + 2H(+) ------> 2Ag(+) + H2O
2011-03-30 01:10:10 補充：
next time, directly add the information directly to the questin.
silver chloride is white; question says the precipitate is yellow.
2011-03-31 12:39:48 補充：
oops, sorry for overlooking.
yes test 3 could show silver ion.
to avoid ambiguity, barium nitrate could be used.
or, add a further test with sodium chloride, testing for insoluble chloride, like silver and lead.
收錄日期: 2021-04-20 00:23:42
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