Solution Preparation by Dilution

If a solution is to be prepared by diluting another solution, whether high precision and accuracy are important or not, the dilution equation, Equation (4.2), is again used  

and A have the same meanings as they do in Equation (4.2). For solution preparation, VB, the volume of the solution to be diluted (the volume before dilution), is calculated so that the analyst can know how much of this more concentrated solution to measure out in order to prepare the less concentrated solution. Remember that VB and VA can have any volume unit, but the units for both VB and VA must be the same (for example, milliliters). The same is true of the concentration units. 

How many milliliters of 12 M hydrochloric acid are needed to prepare 500.0 ml of a 0.60 M solution Solution 4.9 

Rearranging the dilution equation to calculate VB, we have the following  

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To the aqueous suspension of the palladized charcoal catalyst thus obtained are added 20.8 kg of 3-cyano-pyridine (96% purity) and then are added 70 liters of a hydrochloric acid solution prepared by diluting 30 liters of 36% HCI with 40 liters of water. This represents approximately 1.75 mols of HCI for each mol of 3-cyano-pyridine. The suspension is maintained at 10° to 15°C and stirred continuously while introducing a current of hydrogen at a pressure of 3 to 5 psi. When absorption of hydrogen ceases and the 3-cyano-pyridine is completely reduced, the reaction mixture is filtered to remove the catalyst. 

Ammonia-cyanide-sulphite solution. Prepare by diluting 35 mL of concentrated ammonia solution and 3.0 mL of 10 per cent potassium cyanide solution (CAUTION) to 100 mL and adding 0.15 g of sodium sulphite. 

To calculate the strength of a solution prepared by diluting a solution of known quantity and strength, a proportion may be set up as follows ... 

Take up each dye residue in one or two drops of ammonia solution (prepared by diluting 1 mL of concentrated ammonium hydroxide to 100 mL). Using open-ended capillary tubes, spot each color onto both a cellulose TLC plate and a silica gel TLC plate at about 3 cm from the bottom edge. 

Readings were taken at 299 nm of the sample solutions with and without standard addition against the reference solution prepared by diluting the sample extract with O.IMHCI. 

Irradiation Procedure. 30% w/w solutions of poloxamer were prepared in distilled water by the cold process and saturated with nitrous oxide. This agent is a known scavenger of hydrated electrons and is known to enhance crosslinking of poly(oxyethylene) chains (9). Vials containing these solutions were irradiated at ambient temperature in a 2000 Ci ° Co source at a dose rate of 0.5 Mrad h- Physicochemical measurements were performed on solutions prepared by dilution of these irradiated samples. 

Calculation of pH from Concentration of Strong Acid Calculate the pH of a solution prepared by diluting 3.0 mL of 2.5 m HC1 to a final volume of 100 mL with H20. 

A. Place about 3 g of powdered sample in a glass-stoppered Erlenmeyer flask containing 10 mL of dilute hydrochloric acid (5%), boil for 30 s, and cool to room temperature. Add 100 mL of iodine TS, stopper, and shake vigorously for 30 s. Filter through Whatman No. 2 filter paper, or equivalent, discarding the first portion of filtrate. Compare 50 mL of the subsequent filtrate with a reference solution prepared by diluting 10 mL of iodine TS to 50 mL with water, but not treated with carbon. The color of the carbon-treated iodine solution is no darker than that of the reference solution, indicating the adsorptivity of the sample. 

Iodate Dissolve 1.1 g of sample in sufficient ammonia- and carbon dioxide-free water to make 10 mL of solution, and transfer to a color-comparison tube. Add 1 mL of starch TS and 0.25 mL of 1 A sulfuric acid, mix, and compare the color with that of a control containing, in each 10 mL, 100 mg of Potassium Iodide, 1 mL of standard iodate solution (prepared by diluting 1 mL of a 1 2500 solution of potassium iodate to 100 mL with water), 1 mL of starch TS, and 0.25 mL of 1 N sulfuric acid. Any color in the sample solution does not exceed that in the control. 

Transfer 500 mg of (//-menthol into a clean, dry test tube, and add 10 mL of potassium permanganate solution (prepared by diluting 3 mL of 0.1 N potassium permanganate to 100... 

Test for reducing agents Acidify 5 drops of the soda extract with dilute sulphuric acid and add 3 drops of dilute sulphuric acid in excess. Add 2-3 drops of dilute potassium permanganate solution (prepared by dilution of 1 drop of... 

Reduction. The nitro compound is reduced by means of a concentrated solution of sodium hydrosulfide, NaSH, the preparation of which was described on page 113. A test is made in the following way to determine how much of the reducing agent is required 25 cc. of the filtered solution of the nitro compound is pipetted into a 750-cc. Erlen-meyer flask, diluted with 350 cc. hot water, and neutralized with soda to the point where the red coloration, which is formed, just persists. A sodium hydrosulfide solution, prepared by diluting 10 cc. of the concentrated solution to 100 cc., is then added, at 60-70°, from a burette until the color of the solution turns to a piure blue. Additional 1-cc. portions of the hydrosulfide solution are added until a definite blackening is obtained when the colorless spot on filter paper, formed by a salted-out test sample, is treated with ferrous sulfate. From the amount of hydrosulfide used in the test determination, the amount required for the total volume of the nitro solution is calculated. 

Calculate the percent by mass of solute in a solution prepared by diluting 15.95 g of 15.00% stock solution with 100.00 g of water. 

The calibration is established from solutions prepared by diluting a solution of I 000 mg/1 of the element to be determined. When sample solutions are prepared using the fusion method, the reference solutions used for this analysis contain the same quantity of lithium metaborate as the sample solution. The origin of the calibration curve is determined by a blank test solution prepared in the same way as the standards, but without the element to be determined. 

Example 3.6. Diprotic System Ampholyte Calculate the equilibrium pH of a solution prepared by diluting 10 mol of sodium hydrogen phthalate to 1 liter with water ... 

Volume percent is commonly used to specify the concentration of a solution prepared by diluting a pure liquid compound with another liquid. For example, a 5% aqueous solution of methanol usually describes a solution prepared by diluting 5.0 mL of pure methanol with enough water to give 100 mL. 

This experiment supports the classroom discussion of solution preparation by dilution and the dilution calculations involved. It also reintroduces the topic of atomic spectroscopy, which may have been mentioned first in a discussion of electron configurations. 

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