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### Constant Pressure/Volume

Posted: Wed Feb 06, 2019 4:56 pm
Hello,

Dr. Lavelle went over a question in class last week that said "an exothermic reaction occurs an open beaker producing a net 8 moles of gas at 25 C. What is the change in internal energy?"

How do we know that this reaction is occurring under conditions of constant pressure?

Thanks!

### Re: Constant Pressure/Volume

Posted: Wed Feb 06, 2019 8:12 pm
Hi, I just checked my notes and i wrote "assume P=1 atm, use PV=nRT), meaning the pressure is constant at 1 atm. Maybe he only said this verbally or something and it wasn't on the slides and you might have missed it? I hope this helps!

### Re: Constant Pressure/Volume

Posted: Wed Feb 06, 2019 8:14 pm
Also, the pressure has to be constant in an open beaker because the pressure in the beaker would equal the atmospheric pressure, which is constant.

### Re: Constant Pressure/Volume

Posted: Sat Feb 09, 2019 2:51 pm
If the pressure is not stated, it is assumed to be 1 atm. So in this case, it is assumed that the pressure is constant at 1 atm.

### Re: Constant Pressure/Volume

Posted: Sun Feb 10, 2019 4:13 pm
So if pressure is not given, can we assume that it will remain constant at 1 atm?

### Re: Constant Pressure/Volume

Posted: Sat Feb 16, 2019 4:40 pm
"Open beaker" implies constant pressure of 1 atm.

### Re: Constant Pressure/Volume

Posted: Wed Feb 20, 2019 6:03 pm
If the reaction is taking place in an open beaker, pressure will be constant