They are atoms like hydrogen oxygen or nitrogen
Three peaks corresponding to Cl+2 will be recorded. The peaks are for isotope 35, both 35 and 37 and for isotope 37. Mass spectrometer has the ability to detect and separate isotopes, even those differing by a single atomic mass unit. When chlorine isotopes are analysed by mass spectrometer, either peak M or M+2 can be obtained. The intensity ratio in the isotope pattern depends on the natural abundance of the isotopes.
I'm assuming that by "miles" you mean moles.
If O2 is the excess reactant, that means Fe is the limiting reactant. That means that the amount of product being formed depends on the amount of Fe reactant present. To calculate the moles of Fe2O3 formed, start with the given 6.4 moles of Fe and use the mole to mole ratio given by the reaction as shown below:
6.4 mol Fe x

=
3.2 mol Fe2O3
Also, remember, light energy (from the sun) is a reactant for photosynthesis. The plant uses water sunlight and carbon dioxide to make sugars as well as oxygen. Plants, the organisms that carry out photosynthesis, are typically the first ate organism is a Food chain and so most other organisms energy came from the plant somehow. But the plant got its energy from the sun.