The correct answer is option 4, which states that one gram of hydrogen would have the highest number of molecules. To understand why this option is correct, we need to look at the concept of molar mass.

Molar mass is the mass of one mole of a substance, given in grams. One mole of a substance contains Avogadro`s number of particles, which is approximately 6.022 x 10^23 particles.

To calculate the number of molecules in a given mass of a substance, we use the equation:

Number of molecules = (Mass of substance)/(Molar mass of substance)

In this case, we are comparing the number of molecules in 10 grams of carbon dioxide, 10 grams of oxygen, 5 grams of ammonia, and 1 gram of hydrogen.

The molar mass of carbon dioxide is approximately 44 grams/mol, so 10 grams of carbon dioxide would contain approximately (10g)/(44g/mol) = 0.227 moles. Since one mole contains Avogadro`s number of particles, 10 grams of carbon dioxide would contain approximately (0.227 mol) x (6.022 x 10^23 molecules/mol) = 1.368 x 10^23 molecules.

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