Question

It has been estimated that $93\%$ of all atoms in the entire universe are hydrogen and that the vast majority of those remaining are helium. Based on only these two elements, estimate the mass percentage of hydrogen in the universe.

• A. $76.86\%$
• B. $23.14\%$
• C. $79.23\%$
• D. $27.14\%$

Answer 1

The correct option is A $76.86\%$

From a basis of 100 moles, moles of $H$ and $He$ atoms are 93 and 7 respectively.
Therefore,
Mass of H = $93\times 1g=93g$
Mass of He = $7\times 4g=28g$
Hence mass percentage of H $=\frac{93}{93+28}\times 100=76.86\%$