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chm2046l - Unknown Scheme 2 I Description A Phase...

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Unknown Scheme: 2 I. Description A) Phase, solubility, color, odor, shape II. Flame Test A) Orange flame Na+ present (possibly K+, NH4+) B) Red flame Ca2+ present (no Na+) C) Purple flame K+ present (possibly NH4+) D) No change in flame color Ca2+, K+, Na+ absent (possibly NH4 present) III. pH Test A) Add a little bit of unknown to a small amount of neutral water B) Fill several vials with test solution and use indicators to determine pH Common pHs for Anions and Cations: pH 1.5: HSO4- present; CO32-, HCO3-, OH- not present pH 2.5: SO42- present pH 3-3.5: Al(H2O)63+ present; CO32-, HCO3-, OH- not present pH 5-6: NH4+ and/or Mg(H2O)62+ present pH 7: Cl- and/or NO3- and/or SO42- and/or K+ and/or Na+ and/or Ca2+ present pH 9-10: HCO3- present; HSO4-, OH-, and Al(H2O)63+ not present pH 10-12: CO32- present; HSO4-, Al(H2O)63+, NH4+ not present pH 13: OH- present; NH4+, Al(H2O)63+, HSO4-, HCO3- not present If unknown is an insoluble compound, use the liquid to test pH pH 7: CaSO4*2H2O pH 9.5: MgCO3 pH 10: CaCO3 pH 10.5: Mg(OH)2 pH 12.5: Ca(OH)2 *Separations are necessary to test for Cations. To Separate, add excess 3-6M NH3+ to separate Mg+ and
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