Hydrochloric acid, solution preparation 1.5 molar

Precursor solutions were prepared by mixing tetraethoxysilane (TEOS), ethanol, HaO and hydrochloric acid in a molar ratio of 1 20 4 0.004 [6]. The PEO-h-PDMS diblock copolymer surfactant (1 to 20 wt%) was added to the sol, the mixture was stirred until a homogeneous solution was obtained and films were deposited on silicon wafers by dip coating [7]. 

The preparation of cyclohexylmagnesium bromide is described on p. 22. The solution may be standardized by titrating against 0.5 N hydrochloric acid, and exactly one mole equivalent is used in the preparation. Five cubic centimeters of cyclohexylmagnesium bromide solution is slowly added to 20 cc. of water, an excess of the standard acid is added, and the excess acid titrated with sodium hydroxide. If 85 g. (3.5 moles) of magnesium, one liter of dry ether, and 571 g. of cyclohexyl bromide (3.5 moles) are used, a solution results which is about 2 molar. 

This is a crystalline product of insulin and an alkaline protein where the protein/insulin ratio is called the isophane ratio. This product gives a delayed and uniform insulin action with a reduction in the number of insulin doses necessary per day. Such a preparation may be made as follows 1.6 g of zinc-insulin crystals containing 0.4% of zinc are dissolved in 400 ml of water, with the aid of 25 ml of 0.1 N hydrochloric acid. To this are added aqueous solutions of 3 ml of tricresol, 7.6 g of sodium chloride, and sufficient sodium phosphate buffer that the final concentration is As molar and the pH is 6.9. 

Calculate the volume of a 36.45% solution of hydrochloric acid (density = 1.50 g/mL) required to prepare 9.0 liters of a 5.0-molar solution. 

A prehydrolysed solution was prepared by refluxing at 342 K for 1 h an ethanolic solution, containing TEOS, water and hydrochloric acid with the following molar ratios TEOS EtOH HC1 H20, 1 3 5 10 5 1. The amount of F127 was dissolved in ethanol and added to the prehydrolysed solution together with the additional water and HC1. The final solution was then stirred for 24 h at room temperature before deposition. The typical final molar ratios were TEOS EtOH HC1 H20 F127, 1 20 0.004 5 0.005. In order to favour... 

L volumetric flask and adding water up to the mark. Another solution was prepared by adding 0.530 g of anhydrous sodium carbonate to a 100.0-mL volumetric flask and adding water up to the mark. Then, 25.00 mL of the latter solution was pipetted into a flask and titrated with the diluted acid. The stoichiometric point was reached after 26.50 mL of acid had been added, (a) Write the balanced equation for the reaction of HCl(aq) with Na2C03(aq). (b) What is the molarity of the original hydrochloric acid ... 

Method. Solutions of amino acids in phosphate buffer (pH 9.3) are mixed with an equal volume of freshly prepared 0.4 M pyridoxal solution (adjusted to pH 9.3) and permitted to stand at 8 °C for 30 min. (The molar ratio of pyridoxal to amino acid should be >75 1.) At this point, 1 ml of sodium tetrahydroborate solution (100 mg/ml in 0.1 N sodium hydroxide) is added and the contents are gently shaken. Excess of sodium tetrahydroborate is destroyed by addition of sufficient hydrochloric acid (pH 1-2) prior to column chromatography. The pyridoxal derivatives are separated on a column (100 X 0.6 cm) of Aminex A-5 ion-exchange resin (Bio-Rad) at a mobile phase flow-rate of 33 ml/h. The eluting solvents consist of 0.2 N buffers at pH 3.40,4.44 and 4.86 and a 0.35 N buffer at pH 5.86 (all of the buffers are sodium citrate). The separation of a number of pyridoxyl-... 

Bis[l-naphthyl] Ditellurium2 To a stirred solution of 0.15 mol of naphthyl lithium in 200 ml of anhydrous diethyl ether under an inert atmosphere are added in small portions 18 g (0.14 mol) of commercial tellurium powder. After completion of the addition, the mixture is stirred and heated under reflux for 30 min and then poured into aqueous 6 molar hydrochloric acid containing ice. This operation must be performed in a well-ventilated hood to avoid exposure to hydrogen telluride. Air is then bubbled through the filtered mixture which is subsequently extracted several times with diethyl ether. The extracts arc dried with magnesium sulfate and evaporated. The residue is recrystallized from petroleum ether (b.p. 20-40°) yield 66% m.p. 119- 122°. Similarly prepared were the following diaryl ditellurium compounds ... 

Bis[4-acetylphenyl] Ditellurium [Grignard Method] 1 The Grignard reagent is prepared from 4.09 g (0.0165 mol) of the 1,2-dihydroxycthane acetal of 4-acetylbromobenzene in 50 ml of tetrahydrofuran and the solution cooled to 0°. 3.15 g (0.025 mol) of powdered tellurium are added and the mixture is stirred in the flask, which is open to the atmosphere, for 10-15 h. 4 Molar aqueous hydrochloric acid is added to pH 2.5 and the ditcllurium compound is extracted with three 50 ml portions of diethyl ether. The combined extracts arc filtered, dried with sodium sulfate, the solvent is evaporated, and the residue is recryslallized from diethyl ether yield 0.36 g (9%, based on bromoacetal) m.p. 104-106°. 

Bis[4-methoxyphenyl] Tellurium Uichloride1 A 0.2 molar solution of 4-methoxybenzenediazonium chloride is prepared from 24.6 g (0.23 mol) of aminobenzene, 150 m/ of half concentrated hydrochloric acid, and 14 g (0.21 mol) of sodium nitrite in 20 ml of water. To the cooled and vigorously stirred dia/onium salt solution are added 27 g(0.1 mol) of tellurium tetrachloride or 16 g (0.1 mol) of tellurium dioxide dissolved in 75 ml of concentrated hydrochloric acid. The temperature of the reaction mixture must not exceed — 5° during this addition. The mixture is stirred at — 5° for 20 min and then filtered. The filter cake is washed carefully with three 50 ml portions of acetone, then with diethyl ether, and finally with petroleum ether. The product, bi 4-methoxybenzenediazonium] hexachlorotellurale, is dried in air yield 52.8 g (86%). 

A solution is prepared which contains 5 X 10 mol of europium(III) chloride in 200 ml. of water. Since this chloride is quite hygroscopic, it is convenient to dilute a calculated volume of standardized ca. 0.5 M aqueous solution to 200 ml. Alternatively, 0.880 g. (2.5 X 10 mol) of europium (III) oxide is dissolved in a small excess of 6 M hydrochloric acid. The resultant solution is evaporated to a small volume to remove excess hydrochloric acid and ultimately diluted to 200 ml. To the solution of europium (III) chloride is added, with stirring, a solution of 4.0 g. (an excess) of benzoylacetone in 50 ml. of 95% ethanol. The resulting suspension is stirred with a magnetic stirring bar while 15 ml. of molar aqueous ammonia is added dropwise over a period of 2 hours. The mixture of product and excess benzoylacetone is filtered, washed with water, and dried in a vacuum desiccator to give approximately 4.4 g. of solid. 

Diluting solutions In the laboratory, you may use concentrated solutions of standard molarities called stock solutions. For example, concentrated hydrochloric acid (HCl) is 12M. Recall that a concentrated soluhon has a large amount of solute. You can prepare a less concentrated soluhon by diluhng the stock soluhon with solvent. When you add solvent, you increase the number of solvent parhcles among which the solute parhcles move, as shown in Figure 15-14, thereby decreasing the soluhon s concenhahon. Would you still have the same number of moles of solute particles that were in the stock soluhon Why ... 

The volume of sodium hydroxide solution required to just completely react with the hydrochloric acid sample is measured. If we know the concentration of the sodium hydroxide solution in moles per liter, then the number of nroles of NaOH added can be calculated (volume X molarity), and so we know the number of moles of HCl in the sample. Therefore, in this relative method, it is necessary to prepare a reacting solution (sodium hydroxide) of accurately known concentration. 

Stock solutions of HCl with various molarities are frequently prepared. Complete Table 14.7 by calculating the volume of concentrated, or 12M, hydrochloric acid that should be used to make 1.0 L of HCl solution with each molarity listed. 

Rinse your buret with several 1-mL portions of an approximately 0.1 M hydrochloric acid, HCl, solution provided on the reagent bench. Then titrate sample 1 until the color of the solution matches that of your prepared stock solution of 0.1 M H3BO3-O.05 M NaCl. Record in TABLE 35.2 the molarity and the volume of HCl solution that you have used. 

Standard solutions of calcium ion used to test for water hardness are prepared by dissolving pure calcium carbonate, CaC03, in dilute hydrochloric acid. A 1.745-g sample of CaCO is placed in a 250.0-mb volumetric flask and dissolved in HCb Then the solution is diluted to the calibration mark of the volumetric flask. Calculate the resulting molarity of calcium ion. 

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