Question

At 16°C a sample of ammonia gas exerts a pressure of 11.7 atm. What is the pressure when the volume of the gas is reduced to one-fourth of the original value at the same temperature


so the inital Temp=16 C
initial Pressure. 11.7
final pressure-unknown
temperature-same

what next?

Answer 1

You omitted some of the problem.
initial T = 16 C
p = 11.7 atm
final pressure = ??, the unknown.
final T = 16 (apparently doesn't change).
initial volume = ?
final volume = 1/4 the original volume.

What I usually do is to assume a value for V1 (a convenient number of 4), that makes the final volume 1 (1/4 of 4 = 1).
Then use P1V1 = P2V2 and solve for P2.

Answer 2

okay thank you

With your information I did
p1v1=p2v2
(11.7)( 4)= P2(1)
my final answer 46.8 atm