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The yellow color which it imparts to solutions is ascribed to the presence of the undissociated base. If, now, an alkali, such as NaOH, is added to this reddened solution, the reverse series of changes takes place. Of the common indicators methyl orange is the most sensitive toward alkalies and phenolphthalein toward acids; the others occupy intermediate positions.
!Answers!: 6.67% NaOH; 84.28% Na CO . A sample of sodium carbonate containing sodium hydroxide weighs 1.179 grams. It is titrated with 0.30 N hydrochloric acid, using phenolphthalein in cold solution as an indicator and becomes colorless after the addition of 48.16 cc. Methyl orange is added and 24.08 cc. are needed for complete neutralization. What is the percentage of NaOH and Na CO ?
NaOH = 1 cc. of H PO solution of which 1 cc. will precipitate 0.01227 gram of magnesium as MgNH PO . Calculate the percentage of KHC H O . !Answer!: 88.67%. A one-gram sample of sodium hydroxide which has been exposed to the air for some time, is dissolved in water and diluted to exactly 500 cc.
To another portion of the solution we will add some caustic soda, NaOH, in order to rob the normal sulphate of alumina of some of its sulphuric acid. But what has all this to do with mordanting? is possibly now the inquiry.
NaOH used = 1.72 cc. 1 cc. H SO = 1.064 cc. NaOH Normal value NaOH = 0.1321 N. !Answer!: 87.72 cc. One gram of a mixture of 50% sodium carbonate and 50% potassium carbonate is dissolved in water, and 17.36 cc. of 1.075 N acid is added. Is the resulting solution acid or alkaline? How many cubic centimeters of 1.075 N acid or alkali will have to be added to make the solution exactly neutral?
!Answer!: 1.152 grams. What weight of cream of tartar must have been taken for analysis in order to have obtained 97.60% KHC H O in an analysis involving the following data: NaOH used = 30.06 cc.; H SO solution used = 0.50 cc.; 1 cc. H SO sol. = 0.0255 gram CaCO ; 1 cc. H SO sol. = 1.02 cc. NaOH sol.? !Answer!: 2.846 grams.
!Answers!: Acid; 1.86 cc. alkali. In preparing an alkaline solution for use in volumetric work, an analyst, because of shortage of chemicals, mixed exactly 46.32 grams of pure KOH and 27.64 grams of pure NaOH, and after dissolving in water, diluted the solution to exactly one liter. How many cubic centimeters of 1.022 N hydrochloric acid are necessary to neutralize 50 cc. of the basic solution?
Who would lose and why? Assuming the impure NaOH used originally in making the titrating solution consisted of NaOH and Na CO only, what per cent of each was present? !Answers!: Customer lost; 3.94% Na CO ; 96.06% NaOH. In the standardization of a K Cr O solution against iron wire, 99.85% pure, 42.42 cc. of the solution were added.
It is desired to dilute a solution of sulphuric acid of which 1 cc. is equivalent to 0.1027 gram of pure sodium carbonate to make it exactly 1.250 normal. 700 cc. of the solution are available. To what volume must it be diluted? !Answer!: 1084 cc. Given the following data: 1 cc. of NaOH = 1.117 cc. HCl.
In titrating solutions of alkali carbonates in the presence of phenolphthalein, the color change takes place when the carbonate has been converted to bicarbonate. In the presence of methyl orange, the color change takes place only when the carbonate has been completely neutralized. From the following data, calculate the percentages of Na CO and NaOH in an impure mixture.
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