Question

How many moles are present in 1.21 X 10^24 molecules of HBr?

Answer 1

One mole of HBr has 6.02 x 1`0^23` molecules of HBr.

1 mole of HBr = 6.02 x 1`0^23` molecules of HBr.-----(a)

X mole of HBr has 1.21 x `10^24` molecules of HBr.

X mole of HBr = 1.21 x `10^24` molecules of HBr------(b)

Taking ratio of (a) and (b)

X / 1 = 1.21 x `10^24` / 6.02 x 1`0^23`

X= 2.009 moles.