Question

This question was from a test and we cannot figure out how to get the correct answer. We already have the concentration and can in theory get to ppm by getting to 10^-6 rather than -4 given, but how does it change from 3.14 to 375 of some decimal combination. Can someone please explain step by step?

The mole fraction of carbon dioxide in dry air near sea level is 3.14×10⁻⁴ where the molar mass of carbon dioxide is 44.010. The concentration of carbon dioxide in the atmosphere is __________ ppm.

375

3.75 × 10-10

0.0375

3.75 × 105

2.67 × 109

Answer 1

Your doubt is quite easy.You can go in the following manner:-

First of all you can get the contribution of carbon-dioxide in the dry air using the formula :-

partial pressure = mol fraction * Total Pressure

Total pressure here will be atmospheric pressure as that of dry air.If given in your problem consider that else 1 atm.

After getting the partial pressure , as we know

PV = nRT;

P/(RT) = n/V (Rearranging the equation)

n/V is concentration so concentration is P/RT use R as 0.0821

enter the required details and you will get the answer in mol/Litre.

To convert it into ppm convert it

into g/L by multiplying it with 44.010

and than multiply it with 1000 to get into ppm

That`s why you will get something decimal combination of 375.