What is the effect of the nature of solvent to the rate of solubility?

Answer 1

As long as all the reactants are completely soluble in the solvent, it will not have a very large effect on the reaction rate. The temperature of the solution is a much more important factor in controlling reaction rates, and increasing the temperature will increase the rate for most reactions. ---------------------------------------------------------------------------------------------------------------

The influence of solvents on the rates of reactions was discovered by Berthelot & Gilles. Let us examine the influence of solvents on the following 3 reactions. 1. (C2H5)3N + C2H5I ---> (C2H5)4 N+ I- 2. N2O5 ---->N2O3 + O2 3. (CH3CO)2O + C2H5OH -----> CH3COOC2H5 + CH3COOH The rate constant for the 1st reaction varied from 0.00018 in hexane to 0.133 in benzyl alcohol and 70.1 in nitrobenzene. The rate constant of the 2nd reaction was more or less the same in different solvents while the influence of solvents on the rate constant of the 3rd reaction was almost the reverse of the 1st reaction. (0.0119 in hexane and 0.00245 in nitrobenzene)

Solvents influence the reaction rates in 3 different manners. 1. Polarity of solvent If the reaction is one in which the products are more polar than the reactants then a polar solvent accelerates the reaction. In reaction (1) the product being a salt is more polar than the reactants which are comparatively less polar. So the reaction is accelerated in the presence of polar solvents like benzyl alcohol. On the other hand if the reactants are more polar than the products like reaction (3), a polar solvent decreases the reaction rate. In general a polar solvent hastens the reaction in the direction of increasing polarity. When both reactants and products are non polar, polarity of solvents will have no influence on the rate of the reaction and the rate is independent of the nature of the solvent which is what happened in reaction (2). 2. Influence of solvation If either the reactant or the product or the activated complex interacts with the solvent, there may be considerable influence on the rate of the reaction. When the reactants interact with the solvent and are solvated leading to lowering the potential energy of the reactants then the activation energy increases lowering the reaction rate. On the other hand if the activated complex interacts with the solvent and is solvated lowering the potential energy, the activation energy decreases and the rate of the reaction increases. If both the activated complex as well as reactants is solvated, the influence of solvent on the rate may not be considerable. The influence of solvation of products will not have any influence on the rate unless it is a reversible reaction. 3.Dielectric constant of the solvent The work done in bringing 2 charges q1 & q2 from infinity to r is given by, W = q1.q2/D r where D is the dielectric constant of the medium and r is the distance between the charges. So in the case of ionic reactions taking place in the presence of solvents, the dielectric constant of the solvent plays a major role. The more the value of D, the more is the ionization. This work is equal to the electrostatic contribution to the increase of Gibb's free energy from the initial to the transition state. If the signs on the charges are same, then work done is positive; if they are different, then it is negative. The logarithm of the rate constant of an ionic reaction varies inversely with the dielectric constant at a given temperature.

Answer 2

The Kinetic models state that to react, molecules must collide. When the concentration increases, more molecules are present, thus, they collide more. This extra kinetic energy meets the potential energy needed to start the reaction which is called the activation energy. As the concentrations increase, the kinetic energy increases and the probability of finding the "right" orientations for colliding reactants also increases. So as the concentrations increase, the rate of reaction increases.
The higher the concentration (known as molarity), the quicker the reaction rate. This is because more concentration means more quantity of reactant, which means more opportunity for collisions to occur between that reactant and any other reactant present. More opportunity for reaction means a faster reaction.

Answer 3

molecules need to collide to react.

if you have a concentrated solution, the molecules will be close together and will colide often, just like 100 people in a small room will bump into each other often.

If you have a dilute solution, the molecules will be far apart and will colide less often, just like 100 people in football stadium.

Answer 4

Increasing the polarity of the solvent increases the reaction rate because the leaving group and carbocation (both very polar species) are better stabilized by polar solvents (like dissolves like).

Answer 5

nature of solvent greatly affects the rate of solubility because substances dissolves in common property of its solvent. A organic substance would only dissolves with organic solvent and the same way to with inorganic substances.

Answer 6

Yes, it does.

A rule of thumb for Chemistry is that a 10 degree (Celsius/Centigrade) rise in temperature will double the rate of a reaction. Dissolving follows a similar pattern.