GATE 2019 CE (CE1) – Question 50

Air Pollution and Municipal Solid Wastes · Air pollution: pollutants, sources, impacts, control and air quality index · 2 marks · Numerical answer

Air at 0°C and 1 atm contains 0.02 ppm NO₂. Its molecular mass is 46 and molar volume at these conditions is 22.4 L. Find equivalent concentration (μg/m³), to two decimal places.

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Correct answer: 41 to 41.10

Explanation

At the stated conditions, concentration in mg/m³ is ppm times molecular mass divided by molar volume in L/mol: $0.02(46)/22.4=0.0410714$ mg/m³. Multiply by 1000: **41.07 μg/m³**.