Group # 10ESPINOSA, Elise Angela H.

MANUEL, Immary Alleivin R.

SALT SAMPLE:Cd(CH3COO)2

LIQUID SAMPLE INCLUDES:Fe2+ (possibly oxidized to Fe3+)

and K+

Soluble in Water

Dissolve a pinch of sample in water

Add a few drops of Sodium Carbonate

Precipitation? Proceed to Step 2.

No Precipitation? Proceed to Anion Preliminary

Tests.

**

Insoluble in Water

Add 3mL of Sodium Carbonate to a small amount of test sample

Heat for 5 mins. Centrifuge and Decant. Use decantate for Anion Test.

Add little Sulfuric Acid

to a small amount of unknown sample

Note all observations like gas and

product formation, change in color, etc.

If no change occurs, warm the test tube.

ANIONS VISIBLE RESULT REACTION EQUATIONCarbonate Gas formation CO32- + 2H + CO2 + H20

Oxalate Gas formation C2O42- + 2H+ H2C2O4

Sulfide Rotten egg odor S2- + 2H+ H2S

Chloride Fumes in moist air Cl- + H2SO4 HCl + HSO4-

Bromide Reddish brown color Br- + H2SO4 HBr + HSO4-

Iodide Violet color; fumes in moist air I- + H2SO4 I2 + H2S H2O

Chromate Yellow to Orange change in color 2CrO42- + 2 H+ Cr2O72- + H2O

Nitrite Evolution of brown fumes NO2- + 4H+ 4NO + 2H2O + O2

ANIONS VISIBLE RESULT REACTION EQUATION

Acetate Gas formation; vinegar-like smell

OAc- + H+ HOAc

Nitrite Evolution of brown fumes; strong odor

4NO3 + 4H2SO4 2SO42- + 4H2O + 4NO2

Add Silver Nitrate.

Precipitation? Centrifuge and Decant (C&D).

Wash the residue with water. Add Nitric Acid.

C&D.

To the decantate,

add Ammoniaand Silver Nitrate.

Yellow ppt = phosphateRed ppt = chromate

Add Ammoniauntil basic to

unknown sample. Ppt? C & D. Discard the residue.

Add Barium Chloride and

Calcium Chloride. No precipitate?

Sulfate, chromate, phosphate and oxalate are absent.

Yellow precipitate? Chromate might be

present. Add HCl until acidic. If

everything dissolved, sulfate is absent.

Carbonate

Disregard if no effervescence occuredin Sulfuric Acid Test

Chromate &

Permanganate

Disregard if unknown sample is colorless

Add Fe(NO3)3.

Formation of blood-red solution confirms thiocyanate.

CNS--

Fe3+ + CNS- FeCNS2+

FeCNS2+ is a complex ion and is responsible for the formation of the blood red solution

I--

Acidify with HNO3. Add Fe(NO3)3 and CCl4. Shake.

Purple layer confirms iodide. If no iodide is present, proceed to bromide confirmatory

test.

If iodide is present, remove CCl4 layer and add new CCl4and Fe(NO3)3. Remove violet CCl4 layer. Repeat until no

iodide is present. Proceed to bromide confirmatory test.

Br--

To the solution from Iodide test, add equal amount of HNO3. Heat then cool in

cold water.

Add CCl4. Shake thoroughly.

Yellowish/Reddish layer confirms bromide. Discard bromide layer. Proceed to Choride

test.

Cl--

Acidify test solution from bromide test with HNO3.

Add water and AgNO3.

White precipitate confirms chloride.

*Iodide, Bromide and Chloride are ionic while CCl4 is non-polar.

*Purple immiscible layer is formed for Iodide. *Yellowish brown immiscible layer is formed for

Bromide (due to oxidation: Br- Br2)*White precipitate is produced for Chloride because

AgCl is formed.

I-, Br -& Cl-

S2-

Place a small amount of unknown sample in a small beaker. Add HCl.

Moisten a small piece of filter paper with lead acetate. Place it on the convex side of a watch glass. Cover the beaker with the watch glass.

Heat gently. If filter paper turns black/silvery, sulfide is present.

S2-

(a) H+ + S2- H2S(b) Pb2+ + S2- PbS(s)

H2S reacts with lead acetate forming PbS which is responsible for the

black/silver color.

CO32-

Prepare a glass medicine dropper with a drop of barium hydroxide suspended at

the tip.

Cover a test tube with unknown sample with the medicine droper. Warm but not boil.

Observe the droplet. If it becomes cloudy/white, carbonate is confirmed.

CO32-

CO2(g) + Ba2+(aq) BaCO3(s) + H2O

*Carbonates are soluble in acids, producing Carbonic Acid

*Addition of barium hydroxide reacts with carbonic acid, forming BaCO3, which

is the cloudy/white precipitate

Add HCl until acidic then add excess HCl. Add BaCl2.

White precipitate confirms sulfate.

SO42-

Sulfates dont easily react but it reacts with Ba2+.Addition of BaCl2 reacts with sulfate forming Barium Sulfate

SO42-(aq) + Ba2+(aq) BaSO4(s)

Add 1M HNO3 until acidic. Add 3M HNO3 until a layer forms.

Add fresh hydrogen peroxide. Shake once quickly.

Formation of blue colorconfirms presence of chromate.

CrO42-

(a) 2CrO42- + 2H+ Cr2O72- + H2O(b) Cr2O72-(aq) + 4H2O2(aq) + 2H+(aq)

2CrO5(aq) + H2O

CrO42-

*Chromates react with acid and is converted to dichromate

*Dichromate reacts with H2O2 which causes the fading of color

Add 16M HNO3 and ammonium molybdate. Warm in a water

bath.

Yellow precipitate confirms phosphate.

PO43-

*Phosphates are generally stable although there are exceptions: FePO4, CrPO4, BiPO4,

Ca3(PO4)2 and AgPO4

*Yellow color is caused by the formation of ammonium phosphomolybdate

PO43-

H3PO4(aq) + 12 MoO42-(aq) + 3 NH4+(aq) + 22H+(aq) (NH4)3PO4 12 MoO3(s) + 12 H2O

Add 6M HOAc and CaCl2. Precipitation? C&D.

Wash precipitate with water. Discard washing. Add water, KMnO4 and H2SO4.

If permanganate color fades in 30 seconds, oxalate is present.

C2O42-

5C2O42-(aq) + 2MnO4-(aq) + 8H+(aq) 10CO2(g) + 2Mn2+(aq) + 4H2O

C2O42-

*Oxalates are soluble in acidic solutions*Addition of permanganate causes the

conversion of oxalate to CO2 gas* Fading of permanganate color is caused by

the CO2 gas

Add 1:1 sulfuric acid to water solutionn. Vinegar-like odor? Acetate is present

No vinegar odor? Add 2 drops ethyl alcohol. Warm gently. Sniff cautiously.

Presence of sweet alcohol smell confirms acetate.

CH3COO--

*Vinegar-like smell is due to the conversion of acetate to acetic acid upon the addition

of sulfuric acid.

CH3COO--

CH3COO- + H2SO4 CH3COOH + HSO4-

Add concentrated sulfuric acid and a grain of ferrous sulfate. Wait for

a few minutes.

A brown ring formation confirms nitrate.

NO3--

NO3--

(a) 3Fe2+(aq) + NO3-(aq) + 4H+(aq) 3Fe3+(aq) + NO(aq) + 2H2O(l)(b) Fe2+(aq) + NO(aq) Fe(NO)2+(aq)

*Nitrate oxidizes Fe2+ to Fe3+

*Nitrogen (IV) oxide gas is produced which is responsible for the brown ring formation

Add 3M HCl.

A cream/whitish precipitated confirms thiosulfate.

S2O32-

S2O32-

S2O32-(aq) + 2H+(aq) SO2(g) + S(s) + H2O

*Thiosulfate decomposes into sulfite and elemental sulfur

*Elemental sulfur, S , is the white precipitate formed

Add 6M HOAc until acidic. Add K3Fe(CN)6. Let it stand for 1

minute.

Add 1 drop FeCl3. Deep red precipitate confirms nitrite.

NO2--

NO2--

(a) HNO2(aq) + Fe2+(aq) + H+(aq) Fe3+(aq)+ NO(aq) + H2O

(b) NO(aq) + Fe2+(aq) Fe(NO)2+(aq)

*Nitrites are converted to nitrous acid whenever an acid reacts with nitrites

*Deep-red solution is caused by complex ion Fe(NO)2+

Add water and sodium oxalate and sulfuric acid/

Color disappearance within 30 seconds confirms

presence of permanganate.

MnO4--

5C2O42-(aq) + 2MnO4-(aq) + 8H+(aq) 10CO2(g) + 2Mn2+(aq) + 4H2O

MnO4-

*Similar to oxalate test*Formation of CO2 gas occurs which cause

the permanganate color to fade

Qualitative Analysis = used in identifying the presence of a substance in an unknown solution

Different concepts and techniques have to be applied

Conclusions are made after every procedure performed

Follow the procedure very carefully and accurately

Observe ALL possible reactions Observe CLEANLINESS at all times so as to prevent

contamination

Work efficiently and precisely in order to minimize human error.

-FIN-