Qualitative Analysis post lab

Topics: Chemical reaction, Chemistry, Ion Pages: 9 (1803 words) Published: January 7, 2014
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Table 1. Known Cations Detection Table

Preliminary Observation of Sample
-Yellowish and murky in color.
-Contains tiny brown particles inside.
-The consistency of the liquid is smooth and fluid.
Cation
Observations

Na+
-Flame test produced orangey –yellow flames for a short period of time only. -Color was faint.
-Solution might have been contaminated.

NH4+
-After adding 10 drops of NaOH to the sample, a muddy brown solution with tiny solid precipitates. -When tested, litmus paper turned from red to blue.

Ag+
-White precipitate forms after centrifuging, which speculates presence of Ag. -After the addition of HNO3 and NH3, a curdy thick white precipitate formed which confirms presence of Ag

Fe3+
-After centrifuging, murky brownish green precipitates formed. -Confirmatory test proved that Fe was present when solution turned blue

Al3+
-After evaporating, dried yellow substances appeared. After centrifuging, gelatinous white precipitate was noticeable. -When HCl, aluminon and NH3 were mixed, “red lake” formed. Cr3+
-No yellow precipitate formed even with the addition of BaCl2.

Ca2+
-Brown precipitate formed after centrifuging.
-No brick-red flame was observed during the flame test.

Zn2+
-After first centrifuging: brownish precipitate formed
-After the addition of K4[Fe(CN)6] and HCl, bluish green solution and blue precipitates formed.

Ni2+
-The solution turned strawberry red after adding a drop of dimethygloxine. Presence of Ni2+ is confirmed.

Table 2. Unknown Cations Detection Table

Preliminary Observation of Sample
-Color is a really light yellow shade. Close to the color of clean oil -Has the consistency of water.
Cation
Observations
Present? (YES/NO)

Na+
-Sample gave out yellow orange sparks. Yellow flames lasted for 5 seconds. -When Fe(II) Sulfate and glyoxime were added, solution turned light brown.

YES

NH4+
-When NaOH was added to the solution, it did not turn the red litmus paper to blue, it remained red.

NO

Ag+
-After adding HCl and centrifuging, the solution remained to be clear in color.

NO

Fe3+
-Adding HCl and K4[Fe(CN)6] to the solution formed gelatinous rusty brown precipitate. -Solution turned bluish green with rusty precipitates.

YES

Al3+
-Gelatinous white precipitates formed.
-“Red lake” was seen when aluminom was added.

YES

Cr3+
-The adding Ba(OH)2 to the solution did not form any yellow precipitate.

NO

Ca2+
-White precipitate formed when ammonium oxalate was added to the solution.

YES

Zn2+
-Upon the addition ofHCl and K4[Fe(CN)6], blue green precipitates formed.

YES

Ni2+
--By adding dimethygloxime, the precipitate stayed white. Strawberry red precipitate was absent.

NO

Table 3. Sulfuric Acid Test on Known Anions

Anion
Observations
(Addition of Sulfuric Acid)
Observations after Heating
Sulfate
No reaction took place
No reaction took place

Nitrate

No reaction took place
-Brown fumes were observed upon heating the sample.
Chloride
-A pungent odor could be smelled from the colorless gas that was produced.

No reaction took place

Iodide
-A yellow supernatant with reddish brown precipitate was formed. Pungent odor like that of a rotten egg was also smelled.

No reaction took place

Bromide
-A pungent odor was released from the gas.
-Orange brown solution with no precipitate was formed.

No reaction took place

Carbonate
-A colorless and odorless gas was produced when the solution was bubbling up.

No reaction took place

Table 4. Known Anions Detection Table

Anion
Observations
Sulfate
After the addition of HCl and BaCl2, white precipitate formed. Nitrate
After adding FeSO4, and H2SO4, a brown ring formed on top of the solution. Chloride
After the addition of AgNO3, a curdy white precipitate was formed. Iodide
A violet hue was observed with the mineral oil, HCl and Cl2 after combining all three with the solution....

References: Gross RB, Tan JA, Abenojar EC, editors. Modern Experiments in General Chemistry II. 3rd ed. Quezon City: Ateneo de Manila University; 2010
Silberberg, Martin S. Principles of General Chemistry. 3rd Ed. New York: McGraw-Hill;
2013
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