Question

1. If your original unknown is colorless, what ions are absent from your unknown?

2. If you get no precipitate with just the 6 M NH3 in step B, what ions are absent from your unknown?

pls help are my answers correct ty

17 Page 4 Aperiment 24. Qualitative Analysis Group III-NI, Mn, Fe, Al, Cr, Zn 1. PROCEDURES A. Observations of Samples. Obtain an unknown and record code. Observe color of unknown solution Common color correlations are: dark blue - CP (ag) yellow - Fe(a) pale pink . Mn(aq) (this is often masked by darker colors) green - Ni(ag) colorless . All(aq) and Zn(n) B. Group III Precipitation. To 3 ml of the solution to be analyzed, add 0.5 mL 6 M HCl and then add 6M NH, until the solution is neutral. Stir thoroughly and verify neutrality on litmus or pH paper. Add 0.5 mL more of 6 MNH, in excess. Stir and let stand for several minutes - it may flocculate even more on standing Note: You are precipitating hydroxides at this point. They have a Mocculant nature. If you have no precipitate at this point, it is likely that your sample contains no Fe3+, Al3+ or Cr3+ Fe3+ (aq) + 3 NH3(aq) + 3 H2O AP+ (aq) + 3 NH,(aq) + 3 H2O Cr3+ (aq) + 3 NH,(aq) + 3 H2O Mn2(aq) + NH3(aq) + HS (aq) Zn2+ (aq) + NH3(aq) + HS (aq) Ni2(aq) + NH3(aq) + HS-(aq) Fe2(aq) + NH3(aq) + HS (aq) - > Fe(OH),(s,rust) + 3 NH4*(aq) - > Al(OH),(s.colorless) + 3 NHA*(aq) - > Cr(OH)3(s.green) + 3 NH(aq) — > MnS(s peach) + NH4+ (aq) -> ZnS(s,white) + NH4+ (aq) - > NiS(s,black) + NH4+(aq) - > Fe(s,black) + NH4+ (aq) Without centrifuging any precipitate, saturate the solution thoroughly with H S by adding 10 - 12 drops of IM thioacetamide, stirring well and heating for 5 minutes in a hot water bath. Again add 0.5 mL 6 M NH3, mix well and warm slightly. Centrifuge the mixture (use two test tubes if volume is too large for one). The decantate is S9 and may be discarded since your samples do not contain group IV ions. The residue is R9 and should be washed with 2 - 3 mL of distilled water to which 2 drops 6 MNH and 2 drops 3 M NH CI have been added. Centrifuge again and discard the washings. Proceed once to the next step. Note: It is important that you do not let R9 dry. Flocculant precipitates are low-density gelatinous precipitates like the insoluble hydroxides. They tend to suspend in the olution rather than settle to the bottom. If the hydroxide is colorless, like aluminum and zinc hydroxide, the colorless precipitate' my not be visible to you unless you watch very carefully. Washing a precipitate involves adding the indicated water or solution -- stirring thoroughly - centrifuging for about 1 nute -- decanting the wash water and discarding it unless otherwise specified.

Answer 1

your answer 2 is right.

- 1. CA nown Answer of original unknown is colourless. then ust, Fest, donat and Ni 2+ ions are absent. ] Alt and 2n2+ ions may be present in colourless sample. 2. Fest, Al3+, ast