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DIMENSIONAL ANALYSIS CHEMISTRY SUPER easy MOLE CONVERSIONS!!

Question : How many moles of O2 are in the sample of 3.6 kilograms of air if 21% of the air is oxygen O2 by mass?

47.25 moles

Explanation:

First we find the amount of O2 in mass in air

That will be = (21/100) x 3.6

This will give us=0.756 kg

Now we want to find the moles, so we convert this mass into grams since we are going to be working with grams= 0.756 x 1000 = 756 grams

Now, to find the number of moles:

moles= mass / molar mass

in this case mass is 756 grams and molar mass of oxygen is 16

So, the mass divided by molar mass would be =756/16= 47.25 moles of O2

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