Question

How many moles of h2so4 will present as residue if 2.0115 ×10^21 number of molecules are removed from 400 mg h2so4.how many moles of h2so4 are left??????

Answer 1

Molecules of H2SO4 in 400mg of it = 400x10^-3/98x 6.02x10^23 = 2.4x10^21.

NOW

2.4x10^21-2.01x10^21 = 0.39x10^21

So 0.39x10^21 are left

No of moles that will be left

(0.39 is approximately 0.4)

0.4x10^21/6.02x10^23=0.066x10^-2

Or 6.6x10^-4 moles.

I hope this helps you

Incase you still have doubt let me know.