Question

Atomic mass of some elements are given
[Mg=24 O=16]

a) How many atoms are there in 120g Mg?

b) Find the mass of 4x 6.022 x 10^23 oxygen atoms​

Answer 1

Answer:

a) 5 x 6.022 x 10^23 atoms of Mg

b) 64 grams

Explanation:

a) 1 mole = 6.022 x 10^23 atoms

no. of moles = given mass/ molar mass

=>   120/24

->  5

5 x 6.022 x 10^23 is the no. of atoms in 120 gm of Mg.

b) similiarly,

given mass / molar mass = no. of atoms/ avogadro's no. ( = moles)

so,

x/ 16 = 4 x 6.022 x 10^23/ 6.022 x 10^23

avogadro no. gets cancelled out, therefore :-

x = 16 x 4

64

Ans : 64 grams is the mass of the given O atoms.