Question

how many moles are present in 0.55 mg of an electron??

Answer 1

Mass of an electron = 9.1×10^-31 Kg
= 9.1×10^-25 mg .
Then , number of electrons (say X) present in 0.55 mg :
0.55/(9.1×10^-25) = 0.604×10^24
Further ;
no of moles (say n) = X/N
here N is Avogadro's constant .
=> n= 0.604×10^24/(6.023×10^23)
= 1.0034793 .
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hope it helps!

Answer 2

We know that
Mass of electron e = 9.1×10^-31 kg
Number Of electrons in 0.55 mg=0.55/9.1×10^-31=0.604×10^30
Number of moles = number of electrons/Avogadro's number
Number of moles = 0.604×10^30/6.023×10^23= 1003479.3 moles per kg