Solid NaOH

Describe how you would prepare the following three solutions (a) 500 mL of approximately 0.20 M NaOH using solid NaOH (b) 1 L of 150.0 ppm Cu using Cu metal and (c) 2 L of 4% v/v acetic acid using concentrated glacial acetic acid. 

Solid NaOH is always contaminated with carbonate due to its contact with the atmosphere and cannot be used to prepare carbonate-free solutions of NaOH. Solutions of carbonate-free NaOH can be prepared from 50% w/v NaOH since Na2C03 is very insoluble in concentrated NaOH. When CO2 is absorbed, Na2C03... 

Diaminobenzidine tetrahydrochloride (2H2O) [7411-49-6] M 396.1, m >300°(dec), pK ,t(D) --3.3, pKEst(2) 4 7 (free base). Dissolved in water and ppted by adding cone HCl, then dried over solid NaOH. 

Ethylene oxide [75-21-8] M 44.0, b 13.5"/746mm, d 0.882, n 1.3597, Dried with CaS04, then distd from crushed NaOH. Has also been purified by its passage, as a gas, through towers containing solid NaOH. 

Ethyl-4-methylpyridine [529-21-5] M 121.2, b 76 /12mm, 1.510, pK st 6.3. Dried with solid NaOH, and fractionally distd. 

V-[2-Hydroxyethyl]ethylenediamine [2-(2-aminoethylamino)ethanol] [111-41-1] M 104.1, b 91.2°/5mm, 238-240°/752mm, n 1.485, d 1.030, pK 3.75, pK 9.15. Distilled twice through a Vigreux column. Redistilled from solid NaOH, then from CaH2. Alternatively, it can be converted to the dihydrochloride and recrystallised from water. It is then dried, mixed with excess of solid NaOH and the free base distilled from the mixture. It is finally redistilled from CaH2. [Drinkard, Bauer and Bailar 5 Am Chem Soc 82 2992 7960.]... 

Methylpyridine (2-picoline) [109-06-8] M 93.1, b 129.4 , d 0.9444, n 1.50102, pK 5.96. Biddiscombe and Handley [J Chem Soc 1957 7954] steam distd a boiling soln of the base in 1.2 equivalents of 20% H2SO4 until about 10% of the base had been carried over, along with non-basic impurities. Excess aqueous NaOH was then added to the residue, the free base was separated, dried with solid NaOH and fractionally distd. 

CO2 which is also formed (20%) can be removed by passage of the product gas over solid NaOH and the byproduct CuCN can be further oxidized with hot aqueous Fe " to complete the conversion ... 

After cooling, the solution was diluted with 1.5 liters of water and subjected to three extractions with ether. The amine was extracted from the ethereal solution with 2 N HCI and liberated therefrom by the addition of solid NaOH (while cooling). The alkaline solution was extracted with ether and the ethereal solution was dried with soiid NaOH. Distii-lation resulted in 10.6 grams (70% of the theory) of 1-aminoadamantane which, after sublimation, melted at 180° to 192°C (seal capillary). It is converted to the hydrochloride. 

For sodium hydroxide the value of AS° may bo obtained by subtracting the entropy of solid NaOH (given in Table 44) from the values given in Table 45 for the Na+ and OH- ions, which are known independently see Sec. 89. 

Investigation of the reactions of other compounds that have the properties of a base shows that each compound can produce hydroxide ions in water. The OH (aq) ions may be produced directly (as when solid NaOH dissolves in water) or through reaction with water (as when Na2COj and NHj dissolve in water) ... 

Returning to our original 0.100 liter of 1.00 M HQ, let us now consider the addition of 0.101 mole of solid NaOH. Again we have added both H+(aqJ and OH (aq) to the same solution, and the concentrations immediately after mixing do not satisfy the equilibrium expression ... 

C04-0095. Calculate the molarities of all ions present in a solution made by adding 1.53 g of solid NaOH to 215 mL of 0.150 M HCIO4. ... 

C17-0049. Calculate the concentrations ofhydronium and hydroxide ions in a solution prepared by dissolving 0.345 g of solid NaOH in enough water to make 225 mL of solution. 

The pH of the buffer solution, both before and after adding the solid NaOH, is close to the p of the conjugate acid-base pair. Moreover, the pH increases when NaOH is added. The solution becomes more basic as a consequence of the added hydroxide anions. 

C18-0061. How many grams of solid NaOH must be added to the buffer solution described in Problem 18.17 to change the pH by 0.15 units After this NaOH has dissolved, is the solution still a buffer Explain. 

C18-0120. You are doing undergraduate research for a biology professor. Your first assignment is to prepare a pH =7.50 phosphate buffer solution to be used in the isolation of DNA from a cell culture. The buffer must have a total concentration of 0.500 M. On the shelf you find the following chemicals solid NaOH concentrated HCl (12.0 M) concentrated H3 PO4 (14.7 M) KH2 PO4 and K2 HPO4. Write a quantitative detailed set of instmctions that describe how you would prepare 1.5 L of the buffer solution. 

Step 1 Weigh out an amount of solid NaOH and dissolve it in water to obtain a solution with the approximate concentration. 

The calculations for determining the pH at every point in the titration of 1 liter of 0.0200 M CH3COOH with solid NaOH, assuming no volume change, can be divided into 4 types. 

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