Which equation obeys the law of conservation of mass?

2fe + 3o2 → 2fe2o3

4fe + o2 → 2fe2o3

fe + o2 → fe2o2

4fe + 3o2 → 2fe2o3

4Fe + 3O2 → 2Fe2O3

i believe this is the answer

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Explanations:- A balanced equation obeys the law of conservation of mass.

First equation is not balanced as it has two Fe on left side and four Fe on right side.

Second equation is not balanced as it has two O on left side and six O on right side.

Third equation is not balanced as it has one Fe on left side and two fe on right side.

Fourth equation is balanced as it has four Fe and six O on both sides. So, it obeys the law of conservation of mass.

answer is: nuclear fusion produces elements that are heavier than helium.

nuclei combine to form a heavier nucleus, releasing energy.  

for example, fusion of hydrogen atoms at the sun.  

this fusion nuclear reaction is in the inner core of the sun and hydrogen (atomic number 1) is conveted into helium (atomic number 2).  

the inner core is the central region of the sun and all solar energy is produced in the core by nuclear fusion.