Find ΔS° for the formation of CH2Cl2(g) from its gaseous elements in their standard states. Rationalize the sign of ΔS°.

Video transcript

Hello everyone today. We are being asked to use the entropy of formation of the standard states of its elements to identify the change in entropy for the formation of phosphorus oxy chloride. So the first thing we wanna do is we want to reference our standard states of its elements for the following compounds. So we have our phosphorus oxy chloride here Which is in the gas form of course and that's going to be equal to 325.5 jewels per mole kelvin. We then have phosphorus as a solid in white form Which equals 41. jewels per mole kelvin. We of course have oxygen, molecular oxygen and the gas form which is going to be equal to 205.2 jewels per mole kelvin. And lastly we have molecular chloride or cl two in the gas form which is going to have an entropy of 223.1 jewels per mole kelvin. And once again these reference values may be found in your textbook. So the next thing you wanna do put that as step one. The next thing I wanna do is we want to write our out our equation. So we're going to have our phosphorus in the solid form react with half a mole of molecular oxygen in the gas form As well as 3/2 of our chlorine, Our Cl two in the gas form to finally form our phosphorus oxy chloride in the gas form as well. And so to find our change in our entropy for the reaction, we're going to take the standard states of its elements, the entropy for our products and subtract them from our reactant. And so our only product is phosphorus oxy chloride that's going to be 300 and 0.5 jewels Promote Kelvin by itself. And then we're going to subtract that from our entropy values for our reactant. So first we have solid phosphorus which has an entropy value of 0.1 jewels per mole kelvin. We're going to add that to our half More of molecular oxygen entropy. We're just going to be equal to 205. jules promote kelvin. And lastly we're going to add that to our three has entropy for chlorine, gas is going to be 223.1 jewels per mole kelvin. When we plug that into our calculator, we get a final value of negative 152.9 jules per mole. As our final answer. I hope this helped until next time