The chlorofluorocarbon refrigerant trichlorofluoromethane, CCl3F, has Pvap = 100.0 mm Hg at -23 °C and ΔHvap = 24.77 kJ>mol. (b) What is ΔSvap for trichlorofluoromethane?

Video transcript

Hey everyone, we're told that flora form has a vapor pressure of 1605 millimeters of mercury at negative 68 degrees Celsius. If the change of entropy of vaporization of flora form is 16.7 killed jules per mole, calculate its change of entropy of vaporization. To answer this question, we need to use the following formula. The natural log of our pressure two divided by our pressure. one is equal to the negative of our change of entropy of vaporization, divided by our gas constant R Times one over temperature to -1 over temperature one. Now let's go ahead and write out our values our pressure to is going to be our pressure at vaporization or atmospheric pressure. So this is going to be 760 of mercury. Now our temperature one is going to be negative 68.0°C plus 273.15 And this will get us to 205.15 Kelvin. Since we want our temperature to be in Kelvin. And we were also given the change of entropy of vaporization to be 16.7 kg jewels per one mole. Now since our gas constant R is in jewels, we need to use dimensional analysis to convert this into jewels. So we know that per one kg jule we have 10 to the third jewels. This will get us to a value of 16, jewels per mole. Now let's go ahead and plug in the values we have in our question stem and the ones we calculated for. So the natural log of our pressure to Which we said to be 760 of mercury divided by our pressure one Which was told to us to be 1,605 mm of mercury is going to be equal to the negative of 16,700 joules per mole. And this is going to be divided by our gas constant R which is 8. joules per mole times kelvin. Next we're going to multiply this by one over T two which we will calculate for minus one over T one which is 205.15 kelvin. Now when we calculate this we get negative 0.7475606 is equal to negative 2008. Kelvin times one over T two which is our temperature to minus 4.87448 to 086 Times 10 to the negative 3rd Calvin to the negative first. Now when we move these values around and solve for one over T2 we end up with 5.24665 Times 10 to the -3 Kelvin to the negative first, solving for our temperature too We end up with 1 90.60 Kelvin. Now let's go ahead and calculate for the change of entropy of vaporization. So we know that our change in free energy is equal to the change of NLP minus temperature times our change in entropy, our change in free energy is going to be zero and this is going to be equal to the change of entropy of vaporization minus our temperature times the change of entropy of vaporization. Now when we switch this around to solve for our change in entropy of vaporization, this is going to be equal to the change of entropy of vaporization over our temperature. Now when we plug in our values we get 16,700 jewels per mole Divided by 1 90.60 Kelvin and this is going to be the change in entropy of our vaporization. Now when we calculate this out, We end up with a value of 87.6 jewels per mole kelvin and this is going to be our final answer. Now I hope that made sense. And let us know if you have any questions