In which of these cases would it be most useful to use a mole to calculate the number of particles? to calculate the number of atoms in two molecules of water to calculate the number of electrons in five atoms of chlorine to calculate the number of elements in one molecule of naoh to calculate the number of atoms in 5 grams of hcl

it's c (engineer's do their work with mechanical stuff not on any living being)

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.