Molar solutions, preparation

Place 0 5 ml. of acetone, 20 ml. of 10% aqueous potassium iodide solution and 8 ml. of 10% aqueous sodium hydroxide solution in a 50 ml. conical flask, and then add 20 ml. of a freshly prepared molar solution of sodium hypochlorite. Well mix the contents of the flask, when the yellow iodoform will begin to separate almost immediately allow the mixture to stand at room temperature for 10 minutes, and then filter at the pump, wash with cold w ater, and drain thoroughly. Yield of Crude material, 1 4 g. Recrystallise the crude iodoform from methylated spirit. For this purpose, place the crude material in a 50 ml. round-bottomed flask fitted with a reflux water-condenser, add a small quantity of methylated spirit, and heat to boiling on a water-bath then add more methylated spirit cautiously down the condenser until all the iodoform has dissolved. Filter the hot solution through a fluted filter-paper directly into a small beaker or conical flask, and then cool in ice-water. The iodoform rapidly crystallises. Filter at the pump, drain thoroughly and dry. 

If the third substance dissolves in both liquids (and the solubility in each of the liquids is of the same order), the mutual solubility of the liquids will be increased and an upper C.S.T. will be lowered, as is the case when succinic acid or sodium oleate is added to the phenol - water system. A 0 083 molar solution of sodium oleate lowers the C.S.T. by 56 -7° this large effect has been applied industrially in the preparation of the disinfectant sold under the name of Lysol. Mixtures of tar acids (phenol cresols) do not mix completely with water at the ordinary temperature, but the addition of a small amount of soap ( = sodium oleate) lowers the miscibility temperature so that Lysol exists as a clear liquid at the ordinary temperature. 

For many reductions it is not necessary to distil the reagent. Dilute the dark solution, prepared as above to the point marked with an asterisk, to 1 htre with dry isopropyl alcohol this gives an approximately one molar solution. Alternatively, prepare the quantity necessary for the reduction, using the appropriate proportions of the reagents. 

V, mL = volume in milliliters needed to prepare 1 liter of 1 molar solution. 

Calculate the molarity of a potassium dichromate solution prepared by placing 9.67 g of K2Cr207 in a 100-mF volumetric flask, dissolving, and diluting to the calibration mark. 

A number of bridged crown ethers have been prepared. Although the Simmons-Park in-out bicyclic amines (see Sect. 1.3.3) are the prototype, Lehn s cryptands (see Chap. 8) are probably better known. Intermediates between the cryptands (which Pedersen referred to as lanterns ) and the simple monoazacrowns are monoazacrowns bridged by a single hydrocarbon strand. Pedersen reports the synthesis of such a structure (see 7, below) which he referred to as a clam compound for the obvious reason . Although Pedersen appears not to have explored the binding properties of his clam in any detail, he did attempt to complex Na and Cs ions. A 0.0001 molar solution of the clam compound is prepared in ethanol. The metal ions Na and Cs are added to the clam-ethanol solutions as salts. Ultraviolet spectra of these solutions indicate that a small amount of the Na is complexed by the clam compound but none of the Cs . 

What is the molarity of each ion present in aqueous solutions prepared by dissolving 20.00 g of the following compounds in water to make 4.50 L of solution ... 

Self-Test G.1A What is the molarity of sodium chloride in a solution prepared by dissolving 12.0 g of sodium chloride in enough water to make 250. mL of solution ... 

The van t Ho ff equation is used to determine the molar mass of a solute from osmotic pressure measurements. This technique, which is called osmometry, involves the determination of the osmotic pressure of a solution prepared by making up a known volume of solution of a known mass of solute with an unknown molar mass. Osmometry is very sensitive, even at low concentrations, and is commonly used to determine very large molar masses, such as those of polymers. 

A solution prepared by adding 0.50 g of a polymer to 0.200 L of toluene (methvlbenzene, a common solvent) showed an osmotic pressure of 0.582 Torr at 20.°C. What is the molar mass of the polymer ... 

Acrylic resins are polymeric materials used to make warm yet lightweight garments. The osmotic pressure of a solution prepared by dissolving 47.7 g of an acrylic resin in enough water to make 500. mL of solution is 0.325 atm at 25°C. (a) What is the average molar mass of the polymer ... 

EXAMPLE 10.12. (a) What are the molarities of the ions in a solution prepared by dissolving 3.0 mol of AlCl,... 

Add EDC (Thermo Fisher) to the solution prepared in (2) to obtain at least a 5-fold molar excess over the amount of cystamine present. React for 2 hours at room temperature. 

Add the solution prepared in step 2 to the protein solution to obtain at least a 10-fold molar excess of small molecule to protein. In the case of the peptide-protein immunogen conjugate, add the 500 pi of peptide solution to the 200 pi of protein solution. 

Add the solution prepared in step 2 to the protein solution to obtain at least a 10-fold molar excess of small molecule to protein. 

Add 200 mg of sodium carbonate per ml of the dendrimer solution prepared in step 1 and a quantity of epibromohydrin equal to a 285-fold molar excess over the amount of... 

Add 50 pi of the NHS-LC-biotin solution in DMF to each ml of the protein solution in two aliquots apportioned 10 minutes apart. Alternatively, add a quantity of the sulfo-NHS-biotin solution prepared in water to the protein solution to obtain a 12- to 20-fold molar excess of biotinylation reagent over the quantity of protein present. For instance, for an immunoglobulin (MW 150,000) at a concentration of 10 mg/ml, 20 pi of the sulfo-NHS-biotin solution (8 X 10-4 mmol) should be added per ml of antibody solution to obtain a 12-fold molar excess. 

Add a quantity of the biotin-PEG -amine solution to the solution containing the car-boxylate molecule to achieve the desired molar excess. For molecules containing a single carboxylate to be modified, a 1.5- to 2-fold molar excess may be sufficient. However, for proteins or peptides that also contain competing amines, a much larger excess of biotin compound should be used (e.g., 100-fold excess). For instance, for protein biotinylation, add 120 pi of the biotin-PEG -amine solution per ml of the solution prepared in Step 1. 

Light scattering and electron microscopy studies of aqueous PVME solutions and PVME microgels were carried out by Arndt et al. [329,330]. They noted that the Mw of PVME in water was always higher (up to 20 times) than its value (Mw = 46 000gmoH) determined in organic solvent (butanone), even for dilute aqueous PVME solutions well below the phase-separation temperature [330]. Moreover the molar masses of the polymer in water depended on solution preparation conditions. The authors concluded that PVME does not exist as isolated chains in water, but forms loose aggregates (Rh = 200-220 nm) which decrease in size as the solution temperature passes... 

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. 

In preparing a specific molar solution, you should dissolve the required amount of solute in a little solvent and then dilute to the required volume. 

In preparing a molar solution, the correct number of moles of solute (commonly converted to grams using the molar mass) is dissolved and diluted to the required volume. 

A solution prepared by dissolving 7.95 mg of a gene fragment in 25.0 mL of water has an osmotic pressure of0.295 torr at 25.0°C. Assuming the fragment is a nonelectrolyte determine the molar mass of the gene fragment. 

Solution preparation, standardization, and sample analysis activities all involve solution concentration. Let us review molarity and normality as methods of expressing solution concentration. 

It should be stressed that the pH value of an actual buffer solution prepared by mixing quantities of the weak acid or base and its conjugate base or acid based on the calculated ratio will likely be different from what was calculated. The reason for this is the use of approximations in the calculations. For example, the molar concentration expressions found in Equations (5.23) to (5.30), e.g., [H+], are approximations. To be thermodynamically correct, the activity of the chemical should be used rather than the concentration. Activity is directly proportional to concentration, the activity coefficient being the proportionality constant ... 

Suppose you followed the procedure in Example 5.12, but did not weigh exactly 1.861 g, but came close with 1.9202 g. What is the molarity of the EDTA solution prepared with this weight of solute ... 

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