Phenolphthalein indicator

Dissolve or suspend 0 - 5 g. of the acid in 5 ml. of water in a small conical flask, add a drop or two of phenolphthalein indicator, and then 4-5 per cent, sodium hydroxide solution until the acid is just neutrahsed. Add a few drops of very dilute hydrochloric acid so that the final solution is faintly acid (litmus).f Introduce 0-5 g. of p-bromophenacyl bromide (m.p. 109°) dissolved in 5 ml. of rectified (or methylated) spirit, and heat the mixture under reflux for 1 hour if the mixture is not homogeneous at the boiling point or a solid separates out, add just sufficient alcohol to produce homogeneity. [Di- and tri-basic acids require proportionately larger amounts of the reagent and longer refluxing periods.] Allow the solution to cool, filter the separated crystals at the pump, wash with a little alcohol and then with water. Recrystallise from dilute alcohol dissolve the solid in hot alcohol, add hot water until a turbidity just results, clear the latter with a few drops of alcohol, and allow to cool. Acetone may sometimes be employed for recrystallisation. 

Dissolve (or suspend) 0-25 g. of the acid in 5 ml. of warm water, add a drop or two of phenolphthalein indicator and neutralise carefully with ca. N sodium hydroxide solution. Then add 2-3 drops of ca. O lN hydrochloric acid to ensure that the solution is almost neutral (pale pink colour). (Under alkaline conditions the reagent tends to decompose to produce the evil-smelling benzyl mercaptan.) If the sodium salt is available, dissolve 0-25 g. in 5 ml. of water, and add 2 drops of ca. 0 -hydrochloric acid. Introduce a solution of 1 g. of S-benzyl-iso-thiuro-nium chloride in 5 ml. of water, and cool in ice until precipitation is Dibasic and tribasic acids will require 0-01 and 0-015 mol respectively. 

The sodium sulphite solution may also be prepared by dissolving 100 g. of pure (or a corresponding quantity of commercial) sodium hydroxide in about 125 ml. of water, and then diluting to 750 ml. The flask is cooled in running water, a few drops of phenolphthalein indicator are added, and sulphur dioxide passed in until the pink colour just disappears (it is advisable to add a further 1-2 drops of the indicator at this point) and then for 2-3 minutes longer. It is best to remove a sample for test from time to time, dilute with 3-4 volumes of water, and test with I drop of phenolphthalein. 

Phenolphthalein (indicator) dissolve 1 g in 60 mL of alcohol and dilute with water to 100 mL pH range colorless 8.2-10.0 red. 

To approximately 20 ml of a 1 1 mixture of toluene (xylene) isopropyl alcohol, add 1 ml of oil-base mud and 75 to 100 ml of distilled water. Add 8 to 10 drops of phenolphthalein indicator solution and stir vigorously with a stirring rod (the use of a Hamilton Beach mixer is suggested). Titrate slowly with H SO, (N/10) until red (or pink) color disappears permanently from the mixture. Report the alkalinity as the number of ml of H SO (N/10) per ml of mud. Lime content may be calculated as... 

Electrolysis of potassium iodide (Kl) solution. The electrolysis of aqueous Kl is similar to that of aqueous NaCI. The cathode reaction (left/ is the reduction of water to H2(g) and OH-, as shown by the pink color of phenolphthalein indicator in the water. The anode reaction fright) is the oxidation of l (aq) to Ijfaq), as shown by the brown color of the solution. 

For the hydrolysis, accurately weigh approximately 2 g of the fat or oil into a 250 mL conical flask with a ground-glass joint and add 25 mL of the potassium hydroxide solution. Attach a reflux condenser and heat the flask contents on a steam bath for 1 h with occasional shaking. While the solution is still hot add phenolphthalein indicator and titrate the excess potassium hydroxide with the 0.5M hydrochloric acid (record as titration b mL). 

Liebscher and Eppert [100] reported a method for the determination of disulfonates in AOS by titration with Hyamine 1622 in water-trichloromethane-containing phenolphthalein indicator to give vinylsulfonate and total sulfonate concentrations, which are used to calculate disulfonate concentrations. One determination requires 30 min. 

X 10 4 M HCl(aq) with phenolphthalein indicator to see how much NaOH was left unreacted. They found that 30.2 mL of HCl(aq) was required to reach the stoichiometric point, (a) Write the balanced chemical equation for the reaction of S02 and water, (b) What amount of NaOH (in mol) had reacted with the SO, (c) What was the concentration of sulfur dioxide in the air, in parts per million ... 

Ethyl phenylethylmalonate. In a dry 600 ml. round-bottomed flask, fitted with a reflux condenser and guard tube, prepare a solution of sodium ethoxide from 7 0 g. of clean sodium and 160 ml. of super dry ethyl alcohol in the usual manner add 1 6 ml. of pure ethyl acetate (dried over anhydrous calcium sulphate) to the solution at 60° and maintain this temperature for 30 minutes. Meanwhile equip a 1 litre threenecked flask with a dropping funnel, a mercury-sealed mechanical stirrer and a double surface reflux condeuser the apparatus must be perfectly dry and guard tubes should be inserted in the funnel and condenser respectively. Place a mixture of 74 g. of ethyl phenylmalonate and 60 g. of ethyl iodide in the flask. Heat the apparatus in a bath at 80° and add the sodium ethoxide solution, with stirring, at such a rate that a drop of the reaction mixture when mixed with a drop of phenolphthalein indicator is never more than faintly pink. The addition occupies 2-2-6 hours continue the stirring for a further 1 hour at 80°. Allow the flask to cool, equip it for distillation under reduced pressure (water pump) and distil off the alcohol. Add 100 ml. of water to the residue in the flask and extract the ester with three 100 ml. portions of benzene. Dry the combined extracts with anhydrous magnesium sulphate, distil off the benzene at atmospheric pressure and the residue under diminished pressure. Collect the ethyl phenylethylmalonate at 169-160°/8 mm. The yield is 72 g. 

Pour the 25-mL of HC1 into the Erlenmeyer flask and add 2-3 drops of phenolphthalein indicator. Swirl the mixture. 

The concentration of dimethylketene is determined by titration of an aliquot at ice temperatures with 0.1 N sodium hydroxide using phenolphthalein indicator. Under these conditions, blank determinations indicate that ethyl acetate is not hydrolyzed. 

In this method the sample is acidified and the inorganic carbon is removed with nitrogen. An aliquot is resampled for analyses. Buffered persulfate is added and the sample is irradiated in the ultraviolet destructor for about 9 min. The hydroxylamine is added and the sample stream passes into the dialysis system. The carbon dioxide generated diffuses through the gas-permeable silicon membrane. A weakly buffered phenolphthalein indicator solution is used as the recipent stream, and the colour intensity of this solution decreases proportionately to the change in pH caused by the absorbed carbon dioxide... 

Phenolphthalein is colourless and clear in acidic solutions, but imparts an intense puce pink colour in alkaline solutions of higher pH, with k(max> = 552 nm. The coloured form of phenolphthalein contains a quinone moiety in fact, any chromophore based on a quinone has a red colour. But if a solution is prepared at pH 7 (e.g. as determined with a pH meter), we find the phenolphthalein indicator is still colourless, and the pink colour only appears when the pH reaches 8.2. Therefore, we have a problem the indicator has not detected neutrality, since it changes colour at too... 

Give both your acid and base solutions one final shake at this point to ensure their homogeneity. Rinse the buret with 5 to 10 mL of NaOH twice, and then fill it to the top. Open the stopcock wide open to force trapped air bubbles from the stopcock and tip. Allow this excess solution to drain into a waste flask. Bring the bottom of the meniscus to the 0.00-mL line. Using a clean 25-mL pipet (volumetric), carefully place 25.00 mL of the acid solution into each of the three flasks. Add three drops of phenolphthalein indicator to each of the three flasks. 

Add three drops of phenolphthalein indicator to each flask and titrate as before. 

Phenolphthalein indicator changes color in the pH range of 8 to 10. Methyl orange changes color in the pH range of 3 to 4.5. Roughly sketch two titration curves as follows ... 

If phenolphthalein indicator was added to the resulting solution, what would be the color of the solution Explain. 

The resulting solution is basic owing to the presence of the hydroxide ion. The phenolphthalein indicator is pink in basic solutions, so the solution would be pink. 

Procedure Place 2 g of previously dried and accurately weighed sample of tartaric acid in a conical flask. Dissolve it in 40 ml of DW, add a few drops of phenolphthalein indicator and titrate with standardized 1 N sodium hydroxide. Each millilitre of 1 N sodium hydroxide is equivalent to 75.04 mg of C4HgOg. 

Observing and Inferring What did the color change of phenolphthalein indicate ... 

Pour about 10 mL of NH3(aq) into a small beaker. Place the beaker on a sheet of white paper. Add 2 drops of phenolphthalein indicator. 

A few drops of phenolphthalein indicator were added to the Erlenmeyer flask. 

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