How many moles of acetylene (C2H6) had occupy a volume of 3.25L at STP?

The number of moles of acetylene can be found out using the ideal gas law equation

PV = nRT

where P - standard pressure - 101 325 Pa

V - volume - 3.25 x 10⁻³ m³

n - number of moles

R - universal gas constant - 8.314 Jmol⁻¹K⁻¹

T - standard temperature - 273 K

substituting these values in the equation

101 325 Pa x 3.25 x 10⁻³ m³ = n x 8.314 Jmol⁻¹K⁻¹ x 273 K

n = 0.145 mol

number of moles of acetylene are 0.145 mol