Consider the conversion of 1,2-dichloroethane to vinyl chloride, ...

Question

Consider the conversion of 1,2-dichloroethane to vinyl chloride, the starting material for manufacturing poly(vinyl chloride) (PVC) plastics:  Is this reaction spontaneous under standard-state conditions? Would it help to carry out the reaction in the presence of base to remove HCl? Explain. Is it possible to synthesize vinyl chlo-ride from graphite, gaseous H2, and gaseous Cl2 at 25 °C and 1 atm pressure?

Accepted Answer

Hello. In this problem we are told. The following equation shows the process of industrial manufacturing of tetrachloride methane from methane. Were asked to identify the reaction is spontaneous or non spontaneous under standard conditions were asked does the reaction spontaneity change if the reaction is carried out in the presence of sodium hydroxide. And we're also asked is it possible to produce tetrachloride methane from carbon and chlorine? Under standard conditions, Let's begin by answering the first question which is to identify the reaction is spontaneous or non spontaneous understanding conditions. To do that, we will find the change in gibbs free energy. Under standard conditions for this reaction, we do that by adding up the changing groups for energy of formation for the products and subtract off some of the change in gibbs free energy of formation for the reactant. So we need to consult a table to find this thermodynamic data which is only found in the appendix of our textbook. So the change in groups for energy of formation has units of killed joules per mole. I'll write the values for each chemical species underneath them. So for methane is 50.8 chlorine is zero. Tetrachloride. Methane is negative 65.3, and hydrochloride gas is negative 95.3. So we will then put these into our equation to find the change in gibbs free energy for the reaction. Under standard conditions we have one mole of tetra plural methane times. Its value which is 65.3 killed joules per mole. And we have formals Of hydrochloride gas times it's changing gift for energy of formation which is negative 95. kill jules. Now we subtract off our reactant, we have one mole And that same times its value of negative 50.8 killed joules per mole. And we have formals of chlorine, jazz value of zero where standard gibbs free energy of formation. And so this works out then too -395.7 Killed Jules. So our units of moles cancels and we're left with units of kill jules. And so since our change in gibbs, free energy for the reaction is negative and sign, it means that the reaction will be spontaneous under standard conditions. So we've addressed the first question. The next question then asks us, how does the reaction spontaneity changes. Reaction is carried out in the presence of sodium hydroxide. So we first have to determine what happens when we add sodium hydroxide to this reaction. The sodium hydroxide will react with the hydrochloride gas form water and our salt. So we'll write the reaction that will take place. So sodium hydroxide base reacts with our acid. We're gonna break apart our salt into its ions. And then we have our reaction is taking place. The methane reacting with boring gas form, catch a chloral methane and hydrochloride gas. So we're gonna combine these to get an overall reaction. And so we see that we have four hydrochloride gas on the product side of our second reaction. So we're gonna multiply the first reaction through by four to get our hydrochloride to balance. And so now our well of hydrochloride are the same on both the reactant and product side. So those will cancel will now combine everything that remains get our overall reaction. We have methane acting with chlorine gas under basic conditions now form plural methane and our salt same play and four waters. And so we wrote the sodium chloride as the sodium chloride eines. Because when you look for values for the change in gibbs free energy of formation, you won't find it for the salt sodium chloride, but rather you'll find it for the individual ions of sodium and chloride. So we're gonna do like we did above. We're going to calculate then that change in gibbs free energy for this reaction. Again, we will look up values in the table for the change of strategy of formation for methane as we saw above. It's -50.8. Lauren is again zero Setting hydroxide is needed. 419.2 Tetrachloride. Methane is -65.3. sodium is negative 261. and chloride is negative 1 31.3 and water is negative 237.2. So now finding our changing gives energy, understand the conditions for the reaction we have one mole than of teacher methane times its value for the changing gibbs free energy of formation. Under standard conditions, we have formals of sodium Ryan's times its value -261. we have formals of Floridians times its value of negative. I'm sorry, -131.3 told rules per mole. And then we have four moles of water Times its value of -2 and 37.2 kill jules per mole. This takes care of our reactant products. Now we're gonna subtract off our reactant. We have one mole of nothing Times this value negative 50. Plus formals of boring times. This value of zero and then we have formals of Sitting hydroxide and it's changed, it gives information is -419.2. So our moles will cancel and we'll be left with in units of kill jules. This will work out then too -859.3 Killed Jules. And so if we compare this to the previous value, it is more negative, which means that it will increase the spontaneity when we add sodium hydroxide. And then the last question we were asked, deal with whether or not it is possible to produce Tetrick chloral methane from its constituents carbon and chlorine. So if we look at the value for the change in gibbs free energy of formation, protected plural methane. It is negative. So since it is negative in sign, that means that it can be produced from the elements carbon and chlorine. Under standard conditions. Thanks for watching. Hope this helps.

Watch next