[CopperSmurf]

An equivalent definition for compounds in the gas phase, ppm or ppm_v, is the (pressure of the compound) / (total pressure) x 10⁶. The concentration of SO₂ in the air is 49 micrograms/m³ at a temperature of 30 ^oC and 0.8 atm. Now I need to find its concentration in ppm_v

This is what I did:
30 ^oC = 303.15 K
0.0821 L atm / (K mol) = R = gas constant
64 g/mol = MW of SO₂

[49 micrograms/m³ x 1g/10⁶micrograms x 1m³/1000L x 303.15 K x 0.0821 L atm / (K mol) ] / (64g/mol)
= 1.9055 x 10^-8 atm = pressure of SO₂

ppm_v = (as defined above) = 1.9055 x 10^-8 atm / 0.8 atm x 10⁶ = 2.38 x 10^-2

clearly I must've made a mistake somewhere because 2.38 x 10^-2 is not the answer and neither is 23.8
help anyone?

[Borek]

clearly I must've made a mistake somewhere because 2.38 x 10^-2 is not the answer

Is not?

[CopperSmurf]

It's not the answer.    Strange isn't it? Maybe my approach is wrong.

[Borek]

I am hardly perfect, but I got the same result (24 ppb_v).