A 5.00 L sample of helium expands to 12.0 L at which point the pressure is measured to be 0.720atm. what was the original pressure of the gas

The answer to your question is  Pressure 1 = 1.73 atm

Explanation:

Data

Volume 1 = 5 l

Pressure 1 = ?

Volume 2 = 12 l

Pressure 2 = 0.72 atm

Process

To solve this problem use Boyle's law to solve this problem

                 Pressure 1 x Volume 1 = Pressure 2 x Volume 2

-Solve for Pressure 1

                 Pressure 1 = Pressure 2 x Volume 2 / Volume 1

-Substitutiion

                 Pressure 1 = 0.72 x 12 / 5

-Simplification

                Pressure 1 = 8.64/5

-Result

                 Pressure 1 = 1.73 atm