The number of oxygen atoms = 3
Mass = 24 g
<h3>Further explanation</h3>
The formula of a compound shows the composition of the constituent elements
CaCO₃ is composed of 3 types of elements, namely Ca, C and O
The amounts of each of these elements in the compound CaCO₃:
So the number of oxygen atoms = 3
mass of Oxygen :

1) (C2H5)2CBrCH2CH3 is the answer
explaiation:-
so when HBr is added to an alkene , according to the Markonicoff's rule ...H atoms are bonded to the C containing the most amount of H and Br is added to the other C.
2) Just add alkoholic KOH∆
Answer: Pauli exclusion principle: only two electrons can occupy the same orbital and they must have opposite spin directions
Explanation:
1) Zn + 2 HCl = ZnCl2 + H2 ( <span>single replacement )
2) </span>2 NaCl + F2 = 2 NaF + Cl2 ( <span>single replacement )
3) </span>2 AlBr3 + 3 K2SO4 = 6 KBr + Al2(SO4)3 ( <span>double replacement )
4) </span>2 K + MgBr2 = 2 KBr + Mg ( <span>single replacement )
Answer 3
hope this helps!</span>