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An unknown solution acidified with nitric acid gives a white precipitate when tr

ID: 825301 • Letter: A

Question

An unknown solution acidified with nitric acid gives a white precipitate when treated with a few drops of silver nitrate. Is the presence of chloride ion confirmed by this text? What effect, if any, would substituting 6 M HNO3 for 6 M HC1 have on the test for CO3 2- To test for NH4 +, a student placed 1 mL of the unknown solution in a beaker, added 1 mL of NaOH, and covered the beaker with a watch glass to which was attached a moist strip of red litmus paper. The litmus paper remained red. The student then boiled the solution vigorously on a hot plate, hoping to liberate any ammonia gas. The unknown solution didn't contain NH4+, but the litmus paper became spotted with blue. Why?

Explanation / Answer

1)AgCl is the white precipitate formed .

Yes Cl- ion test is confirmed with this reaction because no other precipitates with Ag+ are white other than AgCl....


2) If we add so much concentrated HCl....6M then it would react with the CO32- to completely for the H2CO3 acid


and nothing would be detected ....


However if we added dilute HCl then the reaction would have been


We can test for the carbonate ion by adding dilute
acid
An acid is a substance that forms a solution with a pH value of less than 7. Acidic solutions contain an excess of hydrogen ions, H+(aq).
acid. If the gas given off turns limewater cloudy, then the test is positive. For example, if we add dilute hydrochloric acid to sodium carbonate, sodium chloride is formed and carbon dioxide gas

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