A particular air sample at 1 atm pressure has a density of approximately 1.3 g/liter and contains SO2 at a concentration of 25 µg/m3 . What is this concentration in terms of:
a) Parts per million (mass SO2 per 106 units mass of air)
b) Moles SO2 per 106 mol of air
To find the concentration of SO2 in parts per million (ppm), you need to convert the concentration from µg/m3 to g/L and then divide by the density of the air sample. Here's how to do it:
1. Convert the concentration of SO2 from µg/m3 to g/L:
To convert from µg/m3 to g/L, divide the concentration by 1,000,000. So, 25 µg/m3 = 25/1,000,000 g/L = 0.000025 g/L.
2. Calculate the concentration in parts per million (ppm):
To convert from g/L to ppm, you need to multiply by 1,000,000. So, 0.000025 g/L * 1,000,000 = 25 ppm.
Therefore, the concentration of SO2 in terms of parts per million (ppm) is 25 ppm.
Now, let's calculate the concentration in moles SO2 per 106 moles of air:
1. Convert the concentration of SO2 from µg/m3 to g/L (we have already done this step before):
25 µg/m3 = 0.000025 g/L.
2. Convert the concentration of SO2 from g/L to mol/L:
To convert from g/L to mol/L, you need to divide by the molar mass of SO2. The molar mass of SO2 is approximately 64.06 g/mol. So, 0.000025 g/L / 64.06 g/mol = 3.910 x 10^-7 mol/L.
3. Calculate the concentration in moles SO2 per 106 moles of air:
We need to multiply the concentration by 1,000,000 to convert from mol/L to mol per 106 mol. So, 3.910 x 10^-7 mol/L * 1,000,000 = 0.391 mol per 106 mol.
Therefore, the concentration of SO2 in terms of moles SO2 per 106 moles of air is 0.391 mol per 106 mol.