Chemistry - Mole Concept Question with Solution | TestHub

For the first oxide XO₃,

% of X = $\frac{a}{99.98}\times 100=52$

∴$a=51.98=52$

Thus, the atomic mass $a$ is approximately 52.

For the second oxide X₂O₃,

% of X = $\frac{2b}{99.98}\times 100=52$

$b=25.99=26$

Thus, the atomic mass $b$ is approximately 26.

Element with atomic mass 52 is Cr and 26 is not the atomic weight of any known element. ∴ The oxide is CrO₃