If the amount of gas is decreased and the temperature and pressure stay constant, what will be the effect on its volume?

The volume will increase.
The volume will decrease.
The volume will remain the same.
The volume will be reduced to zero.

3 answers

pv=nRT
v=nR (T/P)
so if n decreases, v decresases if T/P is constant
LOL

Use head, or if that fails use formula for perfect gas

P V = n R T
or
V = n R T/P
if T P and R are the same
V = n * constant
if you decrease n, you decrease V

half the molecules will fit in a half size bottle :)
Heads are sometimes hard to come by.