The universe contains about ten times as many hydrogen atoms as helium atoms,but a helium atom has four times the mass of a hydrogen atom.What is the approximate ratio of the universe's hydrogen to helium by mass?
A) 2.5 to 1
B) 10 to 1
C) 4 to 1
D) 1 to 4

Question

Quizplus · Accepted Answer

The universe has 10 times more hydrogen atoms than helium atoms, but each helium atom is 4 times more massive than a hydrogen atom. Therefore, the mass ratio is 10 hydrogen atoms to 1 helium atom, which is 10:4 by mass, simplifying to 2.5:1.

The Universe Contains About Ten Times as Many Hydrogen Atoms