A gas has a volume of 5 litres at 3 atm. To expand the volume to 7500 ml, what new pressure (in atm) have to be

Boyle's law states that for a fixed amount of gas the pressure of gas is inversely proportional to the volume of the gas at constant temperature.

P1v1 = P2v2

Where P1 is pressure and v1 is volume at first instance

And P2 is pressure and v2 is volume at second instance

Substituting the values

3 atm x 5 L = P2 x 7.5 L

P2 = 2 atm

The new pressure of the expanded volume of gas is 2 atm