Calcium hydroxide constant-volume

Preparation of Sodium Hydroxide from Sodium Carbonate. Dissolve 14 g of anhydrous sodium carbonate in 100 ml of water. Pour the solution into a 250-300-ml round-bottomed flask. Put pieces of broken chamotte crucible on the bottom of the flask (for what purpose ). Fasten the flask in a stand so that a small space remains between the gauze and the bottom of the flask. Heat the solution in the flask up to boiling and add 8-10 g of triturated calcium hydroxide (in small portions). Insert a funnel into the neck of the flask (for what purpose ) and boil the solution during one hour, adding water from time to time to keep the volume constant. After cooling, filter the solution and measure its volume and density. Use the density value to determine the percentage of sodium hydroxide in the solution. Hand in the alkali solution to the laboratory assistant. 

A 225-mg sample of a diprotic acid is dissolved in enough water to make 250. mL of solution. The pH of this solution is 2.06. A 6.9 X 10 AT solution of calcium hydroxide is prepared. Enough of the calcium hydroxide solution is added to the solution of the acid to reach the second equivalence point. The pH at the second equivalence point (as determined by a pH meter) is 7.96. The first dissociation constant for the acid (Ag) is 5.90 X 10 . Assume that the volumes of the solutions are additive, that all solutions are at 25°C, and that Ag is at least 1000 times greater than Ag. 

As indicated in the reaction sequences of equation 1, fractionation of the tritium does occur between the calciiom hydroxide and acetylene formed as products of the initial reaction of the water sample with the calcium carbide. However, the isotopic effect was found by Hohndorf and Oro (14) to be constant at 31.4 1.2 percent, thus indicating that the isotope fraction is independent of chemical yield for the reaction. For the system under consideration, the production of a constant volume of benzene was not attainable due to the restrictions of varying sample size, changes in the efficiency of trimerization due to catalyst depletion from previous samples, and the potential for varying rate of reaction of the water-carbide system. This fact, coupled with the lack of adequately documented tritiated benzene standards, led to the adoption of a system calibration rather than a yield determination for each sample in conjunction with a separate instrument calibration. 

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