I believe the answer is a because 2 times 12 is 24. Hope this helped
Answer: A. There are two hydrogen atoms and one oxygen atom per water molecule.
Explanation:
The chemical formular for water "H2O", means it contain 2 hydrogen atoms and one oxygen atom per molecule.
mass defect = mass of constituents - mass of atom
N has 7p and 9n
proton mass ~ 1.00728 amu
neutron mass ~ 1.00866 amu
electron mass ~ 0.000549 amu
Nitrogen mass ~ 14.003074 amu
mass defect = (7*1.00728)-(7*1.00866)-(7*0.000549)
- 14.003074
= 0.11235amu
convert to energy, the binding energy = 1.68x10^-11 J
c. table salt is a metalloid with properties of both reactants