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2, , ANALYSIS OF COMMERCIAL, SAMPLES, , —= =, , Commercial products from the industries or production units come for consumer sale in the mar,, But before they are marketed, they are tested in the laboratories for their strength and purity., , Acid comes to market in various concentrations. It is checked for its strength against standardig,, base or alkalies., , The alkali is standardised by titrating the known volumes against standard primary acids like sucei, acid. Primary acids are very stable in their strength and purity., , Experiment No. 1, , Strength of Commercial HCI, Aim: To determine the strength of commercial samples of hydrochloric acid., , Theory: Mineral acids like hydrochloric acid or sulphuric acid can be titrated with standardised 0.1), NaOH solution using phenolphthalein indicator to find out it’s strength. The commercial sample of conc, HCI or conc. H,SO, are highly concentrated and their normalities are 11.3 N and 36 N Tespectivel), therefore, they are diluted before titrating with standard alkali solution., , Requirements: Commercial sample of hydrochloric acid, 0.IN NaOH solution, solid succinic acid, 1%, phenolphthalein indicator, 250 cm3 standard measuring flask, 10 cm3/150 cm} pipettes, 50 cm burette,, , conical flasks etc., Procedure:, , Part I: Standardisation of NaOH solution:, =, (1) Prepare 100 cm3 of 0.1N succinic acid. (Dissolve 0.59 g of succinic acid in 100 cm? of distilled, water in a 100 cm} standard measuring flask)., , (2) Fill the 50 cm? burette with rhe supplied NaOH solution., , : 12
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Analysis of Commercial Samples 13, , (3) Pipette out 10 cm} of the diluted succinic acid solution in a 100 cm} conical flask. Add 2 drops, of 1% phenolphthalein indicator to it,, , (4) Titrate the contents of the flask against the supplied NaOH solution from the burette, with, constant shaking till light pink colour is obtained. This is the end point, (x cm)., , Part IL: Titration of Commercial Sample:, , (1) Transfer 2 cm? or the supplied volume of the commercial sample of HCI to a 250 cm} standard, measuring flask., , (2) Dilute it to 250 cm? with distilled water, Shake well., , (3) Pipette out 10 cm} of the diluted solution in a 150 cm} conical flask. Add 2 drops of 1%, phenolphthalein indicator to it., , (4) Titrate it against the standardised NaOH solution from the burette. End point will be from, colourless to light pink colour. (y cm)., , Reactions:, (1) CH,COOH CH,COONa, + 2Na0QH —> | +2H,O, CH,COOH CH,COONa, , (2) HCl + NaOH —> NaCl + H,O, Observations and Calculations:, , Part I: Normality of NaOH solution:, 10 cm} of 0.1N succinic acid solution required x cm? of NaOH solution., , 10x0.1, , , , . Normality of NaOH solution =, =AN., Part II: Commercial Sample of HCI:, 10 cm} of the diluted HC! solution required y cm? of A N NaOH solution., 250 cm? 25 y cm}, , ie, 2 cm} of commercial sample required 25 y cm} of A N NaOH solution., , . . 25yxA, :. Normality of HCI solution = 2, , =BN., G/dm3 of HCl = Normality x Equivalent weight, =B x 36.5, = W gldm’., , , , Results:, (1) Normality of the given commercial sample of HCI = (B) = N., (2) Strength of the given commercial sample of HCI = (W) = g/d,
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Practical Chemistry (FX B.Sc.), , 14 College, Note:, i ial acid (36 N)., 1) Conc. H,S0, is also a commercia oe, 5 Len of ae H,SO, may be diluted to 250 cm} with distilled water. 10 cm3 op tis, solution can be used for titration. oe, (3) H,SO, produces an exothermic reaction while alating it with wa et ,, (4) Dilution should be carried out under the strict supervision of, professor incharge of the hie,, work., (5) Equivalent weight of H,SO, = 49., Experiment No. 2, Strength of an Organic acid (Acetic acid), id by titrimetric method., , Aim: To determine the strength of (acetic acid) an Organic aci, organic acid like sodium benzoate is used in comme,, , Theory: An organic acid like acetic acid or salt of u S, ly. They are tested in the laboratories for their stre,,, , samples like vinegar or food preservative respective!, The reaction between acetic acid and sodium hydroxide is as follows:, , CH;COOH (aq) + OH (ag) —. CH;CO 3/ag) + HO, NaOH solution used in this experiment is standardised against succinic acid which is a priman, standard, non hygroscopic, water soluble crystalline solid., , Requirements: 0.1 N NaOH solution, glacial acetic acid sample, 1% phenolphthalein indicator, 250 ci, standard measuring flasks, 150 cm} conical flasks, 10 cm? pipette etc., , Procedure:, , Part I: Standardisation of NaOH solution:, (1) Prepare 100 cm} of 0.1N succinic acid. (Dissolve 0.59 g of succinic acid in 100 cm? of distilled, , water in a 100 cm standard measuring flask)., (2) Fill a burette with 0.1 N (approximate) NaOH solution., (3) Pipette out 10 cm? of the diluted succinic acid solution in a 150 cm3 conical flask. Add 2 drops, of 1% phenolphthalein indicator to it., (4) Titrate tHe solution against the supplied NaOH solution from the burette with constant shaking, till light pink coloured is obtained. (x cm)., Part II; Estimation of Acetic acid:, (1) Transfer 1.5 cm? the supplied glacial acetic acid solution to 250 cm} with distilled water in a, 250 cm? standard measuring flask. Shake well., (2) Fill the burette with the standardised NaOH solution, (3) Pipette out 10 cm} of the diluted glacial acetic acid solution in a 150 cm conical flask. Add 2, , drops of 1% phenolphthalein indicator to it., (4) Shake well and titrate the glacial acetic acid solution against the standardised NaOH solution,, till the end point is reached. The colour of the solution changes from colourless to pink colour., , (y cm’)
