why is walden's rule applicable only on cations of a large size
Answers
Answer:
ExplanatA plot of 1/Λm vs Λmc can be used to extrapolate 1/Λ0 which is the intercept and 1/K aΛ0 2; the gradient of the line (Fig 5).9 At 5 % viscosity, the K a value is 0.036 which means the equilibrium lies to the right. At 30% viscosity, the K a value is 1.7289 so the equilibrium lies to the left. The number of ions dissociated reflects the molar conductance.
Salt mixtures (Table 2) were carried out and found that the alkyl ammonium ions dominate as the trend is very similar to the alkyl ammonium salt. The large alkyl ammonium ions would undergo ion pairing to any halides in the solution therefore greatly affecting the conductivity (Fig. 6 and 8).
The validity of Walden's Rule can be concluded that at about 30% sucrose solution, the rule starts to break and no longer obeyed. Results showed that conductance of ions is dependent on many factors; the concentration of salt, the viscosity , the ion radius, the mechanism of transport and the size of solvation This affects the relaxation effect, the elctrophoretic effect, the extent of ion pairing, the viscous drag, the retarding force and the electrostatic force. All these factors can alter the mobility of ions which is the key for how conductive the solution is. However, there are many errors in this investigation. The viscosity of the sucrose solutions and the amount of salt added were only an approximate. The solubility for some salts such as NMe 4I are not very soluble in high % viscosities as the solutions are already saturated so not all the salts have been fully dissolved which could induce errors. The temperature of the solutions deviated slightly which could influence the viscosities of the sucrose soultion. As the results were gathered by different groups and each used different apparatus so there could be some calibration errors or human errors.
The investigation could be improved by each groups using the same viscosities so it is easier to compare. The solubility of the salts could be checked before to ensure that the masses of salts added would dissolve in solutions. Temperature of the solutions can be kept at constant by using a water bath so the viscosities errors can be minimised. Other innovation steps could be carried out further such as the effect of temperature, the non- electrolyte used, other salts e.g.: HCl, differences in conductance and Walden's product between weak and strong electrolytes.ion: