Explanation:
one mole of any substance there are 6.022×1023 units of that substance. (This number is called Avogadro's number, NA.)
We need to convert the mass of silicon to moles using the molar mass of silicon, 28.06gmol. This number means that one mole of pure silicon would have a mass of 28.06g. Our given mass, however, is in milligrams; to convert this to grams we'll use the conversion factor 1g103mg:
5.86mg Si(1g103mg)=0.00586g Si
Now, using silicon's molar mass, we'll convert this mass to moles of Si:
0.00586g Si(1mol Si28.06g Si)=2.09×10−4mol Si
Finally, let's use Avogadro's number to convert
