Question

The concentration of NO\(_2\) in the air at NTP is reported as 0.30 ppm (ppm by volume). The concentration of NO\(_2\) in \(\mu g/m^3\) is _______ (rounded off to the nearest integer).

Hint:

To convert ppm to \( \mu g/m^3 \), multiply by the molecular weight and divide by the molar volume at NTP.

Answer 1

Correct Answer: 562

We can use the ideal gas law to convert ppm to \(\mu g/m^3\): \[ \text{Concentration in } \mu g/m^3 = \text{ppm} \times \frac{M}{22.4}, \] where \( M \) is the molecular weight of NO\(_2\), given as 46 g/mol. Substituting the values: \[ \text{Concentration in } \mu g/m^3 = 0.30 \times \frac{46}{22.4} \times 1000 \approx 566 \, \mu g/m^3. \] Thus, the concentration of NO\(_2\) in \(\mu g/m^3\) is \( 566 \).