Thread: AP Chemistry Challenge

AP-level Chemistry challenge question:

Permanganic acid (350 ml of a 2.0M aqueous solution) is reacted with 2.0 L of 2.0 N hydrochloric acid, producing aqueous manganese (II) chloride and chlorine gas. The hydrochloric acid was made with pure radioactive chlorine-33, which has a half-life of 37.24 minutes and undergoes β− decay. The reaction is conducted in a sealed 25 L vessel at an initial pressure of 99.5 kPa. The vessel is kept at a constant temperature of 25°C throughout the reaction. What is the pressure inside the vessel after 75 minutes? What assumptions need to be made when solving this problem?

...and how does that help?

Don't mind him, he's just a spammer. I deleted the post so no one links to his site.

What thoughts have you had about this question? Have you made any progress on it?

well i did the redox half reactions and combined them for an overall reaction of:

MnO4- + 3Cl2 + 8H+ ---> Mn2+ + 4H20 + 6HCl-

so there are 3 moles of gas in the system, and the beta decay, i assumed to be negligible, since it doesnt affect mass. so the initial number of moles, based on

PV=nRT, is 1.004 moles, and since the equation tells us it is 3, I did a ratio to find a pressure of 0.329 atm. But i dont feel that this is correct, and that i forgot stuff