Answer:
We have:
1.204x10^24 atoms of lithium.
The weight of one atom of lithium is: 6.941 atomic mass units.
And we know that:
1 atomic mass unit = 1.661x10^(-24)g
Then the mass of one atom is 6.941 times 1.661x10^(-24)g
m = 6.941*1.661x10^(-24)g = 1.153x10^(-23)g
Then the mass of 1.204x10^24 atoms is 1.204x10^24 times 1.153x10^(-23)g
M = 1.204x10^24 *1.153x10^(-23)g = 1.388x10^(24 - 23) g
M = 1.388x10^1g = 13.88 g
Then 1.204x10^24 atoms of lithium wieght 13.88 grams.
