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Unknown 9-2 - Bryan Merrill Section 7659 Unknown 9A/9B...

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Possible Ions Bryan Merrill Section 7659 Unknown 9A/9B i) Cations: Na + , K + , NH 4 + , Ca 2+ , Mg(H 2 O) 6 2+ , Al(H 2 O) 6 3+ , Zn(H 2 O) 6 2+ , Cu(H 2 O) 6 2+ , Ag(H 2 O) 2 + ii) Anions: Cl , NO 3− , SO 4 2 , HSO 4− , OH (or O 2 ), CO 3 2 , HCO 3− , S 2− , HS iii) Possible insoluble compounds: Ca(OH) 2 , CaSO 4 •2H 2 O, CaCO 3 , Mg(OH) 2 , MgCO 3 , Zn(OH) 2 , ZnCO 3 , ZnS, CuCO 3 , CuO, CuS, Ag 2 CO 3 , Ag 2 O, Ag 2 S, AgCl Preparation before the unknown analysis: i) Prepare the “ Neutral Water ”; (P2−8) ii) Clean glassware and crucible, etc.; iii) Get some indicators, reagents and litmus papers that you need use during the unknown analysis. Notes: 9A (the sample with the numerical label) is a pure salt , which means it only contains two (one cation and one anion) or three ( alums , i.e., two cations and SO 4 2 ) ions. Time limitation for 9A/9B is 120 minutes. 1. Describe Sample : Phase, color, odor, crystal shape if crystalline, etc. 2. Test on Original Sample i) Flame Test Bushy yellow orange Na + Red or red orange Ca 2+ Purple K + Green Cu(H 2 O) 6 2+ No color NH 4 + , Mg(H 2 O) 6 2+ , Al(H 2 O) 6 3+ , Zn(H 2 O) 6 2+ , Ag(H 2 O) 2 + Notes: It is difficult to distinguish the color using solid samples, if you are not sure what color your sample have, you can use the original solution you make or the sample treated with 1M HCl to double check it. ii) NH 4 + Test a) Place a small portion of original sample in a test tube or spot plate, then add a few drop of 1M NaOH solution, at then same time suspend a red litmus paper (before using it, you’d rinse it with deionized water) over the solution. If litmus paper turns blue,
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