`1 xx 10^(21)` molecules are removed from 280 mg of carbon monoxide. Calculate the number of moles of carbon monoxide left.

Explanation

Step 1: To calculate the number of moles of carbon monoxide in 280 mg.
No. of moles of CO `=("Wt. of CO in grams")/("Gram molecular mass of CO")`
`=280/1000 xx 1/28 = 0.01` mol
Step II: To calculate the number of moles of carbon monoixde left.
`6.022 xx 10^(23)` molecules of CO = 1mol.
`1 xx 10^(21)` molecules of CO
`=(1 xx 10^(21))/(6.022 xx 10^(23)) = 0.0016` mol.
No. of moles of CO left= No. of moles of CO taken - No. of moles of CO removed
`=0.01 - 0.0016 = 0.0084`
`=8.4 xx 10^(-3)` mol