Question

From 2mg of calcium 1.2×10^19 atoms are removed find no. of gram atoms left in calcium

Answer 1

Hello! Let me try to answer this :)


-) Mol at first:
= m/Ar
= 2/40
= 0.05 milimoles

-) Number of atoms at first:
= n x L
= 0.05 x 10^-3 x 6.02 x 10^23
= 3.01 x 10^19

-) Number of atoms after it was removed:
= (3.01 - 1.2) x 10^19
= 1.81 x 10^19 atoms

-) Mol after it was removed:
= (1.81 x 10^19)/(6.02 x 10^23)
= 3 x 10^-5 moles

-) No. of gram atoms:
= n x Ar
= 3 x 10^-5 x 40
= 120 x 10^-5 grams
= 1.2 miligrams


Hope this will help you! Thanks and please correct if there are any mistakes ^ ^

Answer 2

Answer:

2 mg Calcium moles =  

40

2×10  

−3

 

​  

=5×10  

−5

 

1 mole =6.022×10  

23

 atoms

x=  

6.022×10  

23

 

1.2×10  

19

 

​  

 

=1.99×10  

−5

 moles removed

∴ Remaining moles =5×10  

−5

−1.99×10  

−5

 

=3.00×10  

−5

 moles

1 g atom =1 mole

Explanation: