Question

what's the percentage of the element CaCo3

Answer 1

percentage of element in CaCO3
calculate mass of the compound
= 40 + 12 + 3 * 16
= 100

Now
% of the Ca
= (40 / 100 ) *100
= 40 %

same carbon

= (12 / 100 ) 100
= 12%

and O
= 48 %