Qualitative Analysis Unknown K Lab

Qualitative Analysis Unknown K Lab - Stephanie Warner Chem...

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Unformatted text preview: Stephanie Warner Chem 153 Shidong Chu 11 November 2005 Qualitative Analysis Unknown K Purpose: To identify various ions in an unknown sample through reactions. Balanced Equations and Discussion: Cations: BaSO 4 + 2NaOH Ba(OH) 2 + 2Na + + SO 4 2- NH 4 + + NaOH NH 3(g) + H 2 O BaSO 4 + C 2 O 4 2- BaC 2 O 4 + SO 4 2 BaSO 4 + H 2 SO 4 BaSO 4 + H 2 SO 4 First I tested my unknown with sodium hydroxide, and it yielded a white precipitate. This didnt really eliminate anything because all of the choices yielded a white precipitate, so I tested it litmus paper and the litmus paper turned blue. When you react NH 4 + with NaOH it forms a gas of NH 3(g) that turns moistened litmus paper from red to blue, so I knew NH 4 + was in my unknown. Then I tested my unknown with potassium oxalate and it produced a white precipitate, just like Ba 2+ does when reacted with C 2 O 4 2- . Then I tested my unknown with a sulfate ion, H 2 SO 4 , and it yielded a white precipitate. This test eliminated Mg 2+ because when Mg 2+ is reacted with H 2 SO 4 there is no reaction. Then I decided to do a flame test of my unknown and it produced a green flame. This meant that Ba 2+ is the other ion in my unknown because the Ca 2+ burns yellow. Anion: SO 4 2- + 2Ag + Ag 2 SO 4 Ba 2+ + SO 4 2- BaSO 4 First I tested my unknown with silver nitrate. This reaction produced a gelatinous solution, so I knew that my anion could not be Cl- because when Cl- reacts with silver nitrate it yields a curdy white precipitate. I also knew that my anion could not be Br- or I- because when both of these ions are reacted with silver nitrate they yield yellow precipitates. I wanted to test my unknown with a barium ion to make sure that my anion was SO 4 2- . When I reacted my unknown with Ba 2+ it produced a white precipitate exactly like the precipitate that forms when SO 4 2- is reacted with Ba 2+ , so I knew my anion was SO 4 2- . Question Set #5 Part 1: Insol in water Burning sulfur odor in H 2 SO 4 green color NaOH green precip Insol in excess NaOH Sol in HCl clear green solution No precip in KI Black precip in Na 2 S White Precip in NaOH Al 3+ No No No--------------------------------------------- Ba 2+ No-------------------------------------------------------------- Bi 3+ Yes No No Yes----------------------------------...
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Qualitative Analysis Unknown K Lab - Stephanie Warner Chem...

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