Which has the greater mass, 1.204 × molecules of molecular hydrogen, , or 1.204 × molecules of water, O?

Question

Which has the greater mass, 1.204 ×  molecules of molecular hydrogen,  , or 1.204 ×  molecules of water,  O?

Quizplus · Accepted Answer

We can use the formula for calculating mass of a molecule, which is:

mass = (number of atoms) × (mass of one atom)

For molecular hydrogen, the mass of one molecule is:

mass = 2 × (mass of one hydrogen atom)
mass = 2 × 1.0079 u
mass = 2.01588 u

Therefore, the mass of 1.204 × 10^82 molecules of molecular hydrogen is:

mass = (1.204 × 10^82) × (2.01588 u)
mass = 2.426 × 10^82 u

For water, the mass of one molecule is:

mass = (mass of one oxygen atom) + 2 × (mass of one hydrogen atom)
mass = 15.999 u + 2 × 1.0079 u
mass = 18.0158 u

Therefore, the mass of 1.204 × 10^82 molecules of water is:

mass = (1.204 × 10^82) × (18.0158 u)
mass = 2.170 × 10^83 u

Since 2.170 × 10^83 u is greater than 2.426 × 10^82 u, we can conclude that option B is correct.

Which Has the Greater Mass, 1