Qualitative Analysis – Acid Base RadicalsAIM: To analyse the given salt for acidic and basic radicals

APPARATUS: Test tubes, test tube holder, required chemicals, burner, beaker etc.

# EXPERIMENT OBSERVATION INFERENCE1 Note the colour of given salt White Cu2+, Fe2+, Fe3+, Ni2+, Mn2+, Co2+ are

absent2 Heat a pinch of salt in a dry test tube Reddish brown gas is evolved NO3

- may be present3 Treat a pinch of salt with dil.H2SO4 No gas evolved CO3

2-, S2-, NO2-, SO3

2- may be absent4 Add a drop of KMnO4 solution in above

solutionPink colour of KMnO4 not discharged

Cl-, Br-, I-, C2O4-, Fe2+ may be absent

5 Heat a pinch of salt with conc. H2SO4 & add a paper pellet

Reddish brown gas is evolved NO3- may be present

6 Heat a pinch of salt with conc. H2SO4 & few copper chips

Reddish brown gas is evolved NO3- confirmed

7 Prepare a paste of the salt with conc. HCl & perform flame test

Apple green flame Ba2+ may be present

8 Mix a pinch of salt with Na2CO3 & heat this on a charcoal cavity

White residue Zn2+, Pb2+, Mn2+ may be absent

9 Heat a pinch of salt with conc. NaOH solution

No gas evolved NH4+ absent

10 Add 1 ml dil. HCl to original solution (OS) of salt

No ppt. Pb+ absent

11 Pass H2S through above solution No ppt. Cu2+, As2+ absent12 To OS add NH4Cl, boil it, cool it & add

NH4OHNo ppt. Fe3+, Al3+ are absent

13 Pass H2S through above solution No ppt. Co2+, Mn2+, Zn2+ absent14 To remaining step 12 solution add

(NH4)2CO3

White ppt. Ca2+, Sr2+, Ba2+ may be present

15 Filter above white ppt., dissolve it in hot dilute CH3COOH. Divide in 2 parts

a) To one part add few drops of K2CrO4 Yellow ppt. Ba2+ confirmedb) Perform flame test on other part Apple green flame Ba2+ confirmed

RESULT: The given salt contains Ba2+ & NO3- radicals

PRECAUTIONS: Take these precautions while performing the experiment-1. Use clean & dry equipments properly2. Handle the chemicals properly

Preparation of solutions(i) Oxalic acid - I

AIM: To prepare 250 ml of 0.1M solution of oxalic acid

APPARATUS: Watch glass, weight box, 250 ml beaker, glass rod, 250 ml measuring flask & wash bottle.

CHEMICALS: Oxalic acid crystals & distilled water

THEORY: Molecular mass of oxalic acid (HOOC—COOH•2H2O) is 126Hence for preparing 1000 ml of 1M solution, 126 g oxalic acid crystals are requiredHence for preparing 250 ml of 0.1M solution,Oxalic acid crystals required = 126/1000 × 250 × 0.1 = 3.15 g

PROCEDURE: Perform the following steps-1. Weigh a clean & dry watch glass accurately & record it in a notebook.2. Weigh 3.15 g oxalic acid on watch glass accurately & record it in the notebook.3. Transfer the oxalic acid into a clean beaker. Wash the watch glass with distilled water to transfer

the sticking particles [Fig I].4. Stir the acid gently with glass rod till it dissolves completely.5. Transfer the solution to a volumetric measuring flask with help of a funnel [Fig II].6. Wash the beaker with distilled water. Transfer the washings into the measuring flask [Fig III].7. Wash the funnel with distilled water transfer sticking solution into measuring flask [Fig IV].8. Add enough distilled water to the flask so as to fill it exactly up to 250 ml.9. Shake the flask gently to make the solution homogeneous.

OBSERVATION: Weight of empty watch glass = w1 gWeight of watch glass with oxalic acid = w2 gVolume of solution prepared = 250 ml

CALCULATION: Weight of oxalic acid = w = w2 – w1 = 3.15 gMolarity of the prepared solution = (w × 1000) ÷ (250 × 126) = 0.1M

RESULT: 250 ml of 0.1M solution of oxalic acid is prepared

PRECAUTIONS: Take these precautions while performing the experiment-1. Use clean & dry equipments.2. Record the measurements accurately.

(ii) Oxalic acid – II

AIM: To prepare 250 ml of 0.1N solution of oxalic acid

APPARATUS: Same as in Oxalic acid – I

CHEMICALS: Same as in Oxalic acid – I

THEORY: Molecular mass of oxalic acid (HOOC—COOH•2H2O) is 126(COOH)2 —→ 2CO2 + 2H+ + 2e-

No. of electrons lost by one molecule of oxalic acid = 2Eq. mass of oxalic acid = Molecular mass/No. of electrons = 126/2 = 63Strength (g/l) = Normality × Eq. mass = 6.3 g/lHence for preparing 250 ml of 0.1N solution,Oxalic acid crystals required = 6.3/1000 × 250 = 1.575 g

PROCEDURE: Same as in Oxalic acid – I

OBSERVATION: Weight of empty watch glass = w1 gWeight of watch glass with oxalic acid = w2 gVolume of solution prepared = 250 ml

CALCULATION: Weight of oxalic acid = w = w2 – w1 = 1.575 gNormality of the prepared solution = (w × 1000) ÷ (250 × 63) = 0.1N

RESULT: 250 ml of 0.1N solution of oxalic acid is prepared

PRECAUTIONS: Same as in Oxalic acid – I

(iii) Na2CO3

AIM: To prepare 250 ml of 0.1M solution of Na2CO3

APPARATUS: Watch glass, analytical balance, weight box, 250 ml beaker, glass rod, 250 ml measuring flask & wash bottle.

CHEMICALS: Na2CO3 & distilled water

THEORY: Molecular mass of Na2CO3 is 106Hence for preparing 1000 ml of 1M solution, 106 g oxalic acid crystals are requiredHence for preparing 250 ml of 0.1M solution,Oxalic acid crystals required = 106/1000 × 250 × 0.1 = 2.65 g

PROCEDURE: Same as in Oxalic acid – I

OBSERVATION: Same as in Oxalic acid – I

CALCULATION: Same as in Oxalic acid – I

RESULT: Same as in Oxalic acid – I

PRECAUTIONS: Same as in Oxalic acid – I

(iv) Mohr’s salt - I

AIM: To prepare 250 ml of 0.05M solution of Mohr’s salt

APPARATUS: Same as in Oxalic Acid – I

CHEMICALS: Mohr’s salt, conc. H2SO4 & distilled water

THEORY: Molecular mass of Mohr’s salt (FeSO4•(NH4)2SO4•6H2O) is 392Hence for preparing 1000 ml of 1M solution, 392 g oxalic acid crystals are requiredHence for preparing 250 ml of 0.1M solution,Oxalic acid crystals required = 392/1000 × 250 × 0.05 = 4.9 g

PROCEDURE: Perform the following steps-1. Weigh a clean & dry watch glass accurately & record it in a notebook.2. Weigh 4.9 g Mohr’s salt on watch glass accurately & record it in the notebook.3. Transfer the Mohr’s salt into a clean beaker. Add 5 ml of conc. H2SO4 to check hydrolysis of

FeSO4. Wash the watch glass with distilled water to transfer the sticking particles [Fig I].4. Stir the solution gently with glass rod till it dissolves completely.5. Transfer the solution to a volumetric measuring flask. Wash the beaker with distilled water &

transfer the washings into the measuring flask.6. Add enough distilled water to the flask so as to fill it exactly up to 250 ml.7. Shake the flask gently to make a homogeneous solution.

OBSERVATION: Weight of empty watch glass = w1 gWeight of watch glass with Mohr’s salt = w2 gVolume of solution prepared = 250 ml

CALCULATION: Weight of Mohr’s salt = w = w2 – w1 = 4.9 gNormality of the prepared solution = (w × 1000) ÷ (250 × 392) = 0.05M

RESULT: 250 ml of 0.05M solution of Mohr’s salt is prepared

PRECAUTIONS: Same as in Oxalic acid – I

(iv) Mohr’s salt – II

AIM: To prepare 250 ml of 0.05N solution of Mohr’s salt

APPARATUS: Same as in Oxalic acid – I

CHEMICALS: Same as in Mohr’s salt – I

THEORY: Molecular mass of Mohr’s salt (FeSO4•(NH4)2SO4•6H2O) is 392Fe2+ —→ Fe3+ + e-

No. of electrons lost by one molecule of Mohr’s salt = 1Eq. mass of oxalic acid = Molecular mass/No. of electrons = 392/1 = 3923Strength (g/l) = Normality × Eq. mass = 19.6 g/lHence for preparing 250 ml of 0.1N solution,Oxalic acid crystals required = 19.6/1000 × 250 = 4.9 g

PROCEDURE: Same as in Mohr’s salt – I

OBSERVATION: Weight of empty watch glass = w1 gWeight of watch glass with Mohr’s salt = w2 gVolume of solution prepared = 250 ml

CALCULATION: Weight of Mohr’s salt = w = w2 – w1 = 4.9 gMolarity of the prepared solution = (w × 1000) ÷ (250 × 392) = 0.05M

RESULT: 250 ml of 0.05N solution of Mohr’s salt is prepared

PRECAUTIONS: Same as in Oxalic acid – I

Titration

AIM: To determine the Normality & strength of X in the given solution, with NYN solution of Y

APPARATUS: Burette, burette stand, pipette, funnel & titration flasks

CHEMICALS: Indicator, N1N solution or Y & distilled water

THEORY: X + Y —→ productsIndicator: ___________Colour change:_______ to ________

PROCEDURE:1. Fill X solution in burette2. Pippete VY ml of Y solution in a conical flask3. Add 2 drops of Indicator into it & place just below the burette4. Note down lower meniscus reading of X solution5. Run X solution drop-wise with constant stirring until permanent colour change is observed6. Note the lower meniscus reading of X solution7. Repeat the steps 2-3 times

OBSERVATION: Initial Reading of burette Final Reading of burette Volume of X used in ml = VX

1.2.3.

CALCULATION: NXVX = NYVY

NX = NYVY/VX

Strength = Normality × Eq. wt. = NYVY/VX × (Eq. wt.)X

RESULT: Normality of X is ___NStrength of X is ___ g/l

PRECAUTIONS: Same as in Oxalic acid – I