Chem
posted by Don .
a container of 2.00 moles of an ideal gas as 1000 K undergoes a constant pressure and volume process in which the number of moles is increased to 5moles. what is the final temperature of the gas.
How do I start this? Do I somehow use the ideal gas law?

Use PV=nRT
so R=P1V1/n1T1
and R=P1V1/n2T2
R=P1V1/n1T1=P1V1/n2T2
n1T=n2T2 
I got the answer to be 400. But can you explain to me those formulas? I'm still a bit confuse on how you got them. Where do these P1 and P2 and T1 and T2 come from

The original formula is
PV=nRT
for the question given we have a set of starting conditions
P=P1
V=V1
n=n1
T=T1
hence
P1 x V1=n1 x R x T1
which rearranges to
R=P1V1/n1T1
the second set of conditions is
P=P1
V=V1
(because P1 and V1 are constant in the question)
T=T2
N=n2
so
R=P1V1/n2T2
as R is the same in both cases
R=P1V1/n1T1=P1V1/n2T2
which rearranges to
n1T=n2T2