Question

Which of the following quantities contains the greatest number of particles?

2 moles of carbon atoms

2 moles of carbon dioxide molecules

2 moles of diatomic oxygen molecules

All of these quantities contain the same number of particles.

Answer 1

All of those quantities contain the same number of particles, since they are all two moles (or 1.204*10^24 particles).

It's similar to asking which one is heavier: a pound of brick, or a pound of feathers. Since they are both one pound, they will weigh the same. 

Hope that helped! :)

Answer 2

Answer: All of these quantities contain the same number of particles

Explanation: according to Avogadro's law, equal volumes of all gases under the same conditions of temperature and pressure contain equal numbers of molecules. According to Avogadro's principle, the number of Particles present in one mole of any substance is equal to 6.02x10^23

Therefore, 2moles will contain 2 x 6.02x10^23 = 1.204x10^24. This will be the same for all the elements listed in the question.