The higher oxide of an element (E) has the formula EO₃. Its hydride contains 2.47% hydrogen.The element is

Higher oxide of an element E is EO₃. so oxidation state of E = +6. as the element has six electrons in its outer shell, element belongs to 16th group. The hydride of group 16 (S, Se, Te) have general formula H₂E.

now 2.47% hydrogen contains in hydride of given element.

so, in 100g of hydride, contains 2.47 g hydrogen.

weight of hydrogen = 2.47

and then weight of element = 100 - 2.47 = 97.53g

now equivalents of element = equivalents of hydrogen

⇒97.53/(atomic weight/2) = 2.47/1

⇒97.53 × 2/2.47 = atomic weight of E

⇒atomic weight of E = 78.97 g/mol.

Therefore the element is Se (atomic weight of Se is 78.97 g/mol).