Chemistry Problems Thermodynamics Blase Ferraris (did these problems for Gangluff) Final Project 1996B and 1997D

What is the sign of ΔS for the reaction? Explain. What change, if any, will occur with ΔG for the reaction as the temperature is increased? Explain your reasoning in terms of thermodynamic principles. If He gas is added to the original reaction mixture at constant volume and temperature, what will happen to the partial pressure of Cl2? Explain. If the volume of the reaction mixture is decreased at constant temperature to half the original volume, what will happen to the number of moles of Cl2 in the reaction vessel? Explain. PCl 5(g)  PCl 3(g) + Cl 2(g) 1997 D

What is the sign of ΔS for the reaction? Explain. Entropy increase will be observed in a reaction in which there is an increase in the moles of gas in the product PCl 5(g)  PCl 3(g) + Cl 2(g) Moles products > moles reactants ΔS is positive

What change, if any, will occur with ΔG for the reaction as the temperature is increased? Explain your reasoning in terms of thermodynamic principles. ΔG° = ΔH° - TΔS° Since ΔS° is positive, increasing T will result in a larger term being subtracted from ΔH°. Or ΔG°= -RTlnK as T increases, ΔG° gets more negative ΔG° will decrease

If He gas is added to the original reaction mixture at constant volume and temperature, what will happen to the partial pressure of Cl 2 ? Explain. Obviously, Helium is not a part of the overall reaction PCl 5(g)  PCl 3(g) + Cl 2(g) (where’s He? Exactly, NO WHERE) Therefore, adding Helium to the reaction wouldn’t affect anything in the reaction at all. *note* Remember, the partial pressure of Cl 2 is its pressure in proportion to the other parts of the chemical equation. Since Helium is not a part of the equation, adding it will affect the overall pressure, but not Cl 2 ’s partial pressure. It won’t tip the reaction in favor of the products or the reactants therefore the reaction itself will remain unaffected.

If the volume of the reaction mixture is decreased at constant temperature to half the original volume, what will happen to the number of moles of Cl 2 in the reaction vessel? Explain. Decrease in Volume leads to an increase in Pressure When pressure increases, the reaction shifts to side of the equation with lesser moles of gas. PCl 5(g)  PCl 3(g) + Cl 2(g) Moles Reactants < Moles Products Therefore PCl 5 will increase and Cl 2 will decrease

MR GANGLUFF DANCING AT PROM