How many moles of gas occupy 98l at a pressure of 2.8atm and a temperature of 292k? and what law would you use?

Let's assume that the gas has ideal gas behavior.

Then we can use ideal gas equation,
PV = nRT

Where, P is Pressure of the gas (Pa), V is volume of the gas (m³), n is the number of moles of gas (mol), R is the Universal gas constant (8.314 J mol⁻¹ K⁻¹) and T is the temperature in Kelvin (K)

The given data for the gas is,
P = 2.8 atm = 283710 Pa
V = 98 L = 98 x 10⁻³ m³
T = 292 K
R = 8.314 J mol⁻¹ K⁻¹
n = ?

By applying the formula,
283710 Pa x 98 x 10⁻³ m³ = n x 8.314 J mol⁻¹ K⁻¹ x 292 K
                                       n = 11.45 mol

Hence,moles of gas is 11.45 mol.