Volume=1600cm³=1.6dm³=1.6L
Temperature=25°C=273+25=298K
Pressure=75000Pa
Now
Apply ideal gas equation
The number of moles needed is
n=48.43mol.
Calculations
Given the values of the volume and temperature, we would convert them to the required units.
Volume=1600cm³=1.6dm³=1.6L
Temperature=25°C=273+25=298K
Pressure=75000Pa
We would use the ideal gas equation
PV=nRT
n=PV/RT
n=75000(1.6)/8.314(298)
n=48.43mol