Chlorine free energy change

Pandey et al. have used ultrasonic velocity measurement to study compatibility of EPDM and acrylonitrile-butadiene rubber (NBR) blends at various blend ratios and in the presence of compa-tibilizers, namely chloro-sulfonated polyethylene (CSM) and chlorinated polyethylene (CM) [22]. They used an ultrasonic interferometer to measure sound velocity in solutions of the mbbers and then-blends. A plot of ultrasonic velocity versus composition of the blends is given in Eigure 11.1. Whereas the solution of the neat blends exhibits a wavy curve (with rise and fall), the curves for blends with compatibihzers (CSM and CM) are hnear. They resemble the curves for free energy change versus composition, where sinusoidal curves in the middle represent immiscibility and upper and lower curves stand for miscibihty. Similar curves are obtained for solutions containing 2 and 5 wt% of the blends. These results were confirmed by measurements with atomic force microscopy (AEM) and dynamic mechanical analysis as shown in Eigures 11.2 and 11.3. Substantial earher work on binary and ternary blends, particularly using EPDM and nitrile mbber, has been reported. 

In this, to the free energy change for the reaction involving the interaction of chlorine and the metal oxide, is added the large value of the free energy of formation of carbon dioxide from its constituent elements. 

At 800 °C, the standard free energy change for the reaction is -45.60 kj. Carbon for reduction and chlorine for chlorination are provided by certain compounds like carbon tetrachloride, and these may be used. Using carbon tetrachloride, the chlorination may be conducted at a lower temperature (650-700 °C) according to the reaction ... 

It follows that titanium tetrachloride can not chlorinate silica because at all temperatures the free energy change for that reaction has a large positive value. In general, in the interaction between the oxide (MO) of one metal (M) and the chloride (M C12) of a different metal (M ) ... 

If the standard free energy change associated with the metal silicate chlorination reaction is given by AG , then... 

If AG has a value which is more negative than that of AG, then AG° becomes more negative than the standard free energy change for the metal oxide chlorination reaction (AG ). An oxide which is difficult to chlorinate in the free state may, therefore, be chlorinated more easily when compounded into a silicate. 

The free energy change for the dissociation of solid silver chloride to yield chlorine gas at the pressure pch is zero, since the system is in equilibrium hence, the free energy change of the second reaction is identical with that for the over-all process. An electrode consisting of chlorine gas at the dissociation pressure peu would thus have the same potential, in a given chloride ion solution, as would the Ag, AgCl(s) electrode. 

The standard free energy change for this reaction is found by combining data from three other reactions. First, the association of hydrogen and chlorine to give HCl gas has the properties... 

When the two electrodes of a cell are interconnected by an external circuit, however, the cell reaction will only occur spontaneously if the free energy change associated with the net cell reaction is negative. This is not the case in a cell for the production of chlorine and caustic soda, i.e. the free energy of reaction (1.11) is positive, and for reaction (T.ll) to occur it will be necessary to supply energy by applying a potential between the two electrodes. This potential must certainly be greater than the difference between the reversible potentials of the cathode and anode in the cell, ( - e ), calculated from... 

THE SOLUTION As was shown in Example 2.7, the overall Gibbs free energy for an electrochemical system is the sum of the free energy changes occurring at the individual electrodes. To illustrate this point, consider the reactions occurring in the chlorine electrolysis of Examples 2.6 and 2.7. At the anode we have numerical results for G (kJ/mol) ... 

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