Nernst Distribution Law Limitations

• Such a case occurs in the distribution of a weak acid (e.g. succinic acid or oxalic acid) between ether and water. • When the distribution of solute X has reached dynamic equilibrium, the rate (R1) at which the molecules pass from X of solvent A to B is proportional to its concentration (C1) in A. The rate (R2) at which the molecules pass from X of solvent B to A is proportional to its concentration (C2) in B. Two important techniques are based entirely on distribution law. • In equilibrium, iodine concentrations in benzene (Cb) and water (Cw) are determined experimentally and the partition coefficient value is calculated. Sb/Sw = KD When distributing succinic acid between ether and water at 15 degrees Celsius, 20 ml of the essential layer contains 0.092 g of acid. Determine the weight of the acid present in 50 ml of the aqueous solution in equilibrium with it if the partition coefficient of succinic acid between water and ether is 5,2. • Similarly, a component with a lower distribution ratio descends later and is received in another vessel. A solid X is added to a mixture of benzene and water. After good shaking and standing, it was later found that 10 ml of benzene contained 0.13 g X and 100 ml of water layer contained 0.22 g X. When a solute is shaken in equilibrium with two immiscible solvents, both solvents are saturated with the solute.

Since solubility also represents concentration, we can write the distribution law as follows: The constant Kd or simple K is called the distribution coefficient or distribution coefficient or distribution ratio. This is the equation of the Nernst distribution law. Since k1 and k2 are constant at the same temperature, the partition coefficient KD is constant even when the temperature is solid – Explain the different applications of the distribution law • The different components of the mixture are extracted by hexane in the order of their distribution coefficients. How is the distribution law modified by the change in molecular state? Application of the law of distribution to normal molecules in both solvents Thus, if the value of the partition coefficient (Kd) and the solubility of the solute in one of the solvents are known, the solubility of the solute in the second solvent can be calculated. If C1 denotes the concentration of the solute in solvent A and C2 denotes the concentration in solvent B, Nernst`s distribution law can be expressed as follows: In 1891, Nernst studied the distribution of several solutes between different pairs of suitable solvents. He gave a generalization that regulates the distribution of a solute between two immiscible solvents. At constant temperature, the ratio of the concentration of a substance in two immiscible liquids present in equilibrium with each other is called the partition coefficient. • Since the distribution ratio at 800º C is about 300 in favor of zinc, most of the silver penetrates the zinc layer. Although this is a very useful law, it also has some limitations • Thus, the component with the highest partition coefficient first descends into the sinking hexane, which is collected separately. • The higher the distribution ratio in favour of the organic solvent, the greater the quantity extracted in one operation • In these cases, the distribution right applies only to the part of the solute present in the form of single molecules. • Since the distribution ratio is in favor of the ether, most of the organic matter passes into the ether layer. The substance can be extracted with ether, where its distribution ratio is twice in favor of ether.

Consider the distribution of I2 between two immiscible liquids, CCl4 and water in the presence of potassium iodide KI. Therefore, in equilibrium, the ratio of the concentration of I2 in the two layers is constant at constant temperature. This constant is called the distribution coefficient and is denoted K. • This is the equation of the distribution law modified during dissociation in one of the solvents. • Applications of the right of distribution in medicinal products • Restrictions on distribution rights include constant temperature, same molecular state, equilibrium concentrations, dilute solutions, immiscibility of solvents • Greater sensitivity can be achieved by using a “distribution indicator”. • If it is constant for different concentrations of iodine, it is confirmed that the formula of the complex I3− • This is stirred with a second portion of the solvent. C1 is the concentration of X in solvent A and C2 is the total concentration of X (dissociated and undissociated) in solvent B. (1) Use of all ether in a batch. Let x grams be the weight of the substance extracted in the solvent layer. Then the amount of substance that remains in the water layer = A – x grams. Therefore, at 25 degrees Celsius, an aqueous iodine solution containing 0.0516 g liter-1 is in equilibrium with a solution of carbon tetrachloride containing 4.412 g liter-1.



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