5. Which sample contains the least number of atoms? A. 2 mol of NaCl
B. 2 mol of NH3
C. 1 mol of CH3COOH
D. 1 mol of H20

Why is the answer a?

2h2o2--> 2h2o + o2

this reaction is of the spontaneous decomposition of hydrogen peroxide down into water and oxygen.

add 2 molecules of hydrogen peroxide and 2 molecules of water. since oxygen is naturally diatomic, the total number of atoms of each element is now the same on both sides of the equation so it is balanced.

this may not be entirely correct but let me know.

the answer to this question is 3.