How many moles in 43 liters of co2 at stp?

Let's assume that CO₂ has ideal gas behavior.

Then we can use ideal gas formula to solve this.
PV = nRT

Where,
   P = Pressure of the gas (Pa)
   V = Volume of the gas (m³)
   n = moles of the gas (mol)
  R = Universal gas constant (8.314 J K⁻¹ mol⁻¹)
  T = Temperature in Kelvin (K)

In this problem,
  P = Standard pressure = 1 atm = 101325 Pa
  V = 43 L = 43 x 10⁻³ m³
  R = 8.314 J K⁻¹ mol⁻¹
  T = standard temperature = 273 K
  n = ?

     PV = nRT
By rearranging,
       n = PV / RT
       n = (101325 Pa x 43 x 10⁻³ m³) / (8.314 J K⁻¹ mol⁻¹ x 273 K)
       n = 1.92 mol

Hence moles of CO₂ gas in 43 L at STP = 1.92 mol