The highest oxide of the element corresponds to the formula EO3. Its hydrogen compound contains 2.47% hydrogen.

The highest oxide of the element corresponds to the formula EO3. Its hydrogen compound contains 2.47% hydrogen. Define this element. Write the formula for its compound with hydrogen.

Since, according to the condition, the higher oxide of the unknown element has the formula EO3, the element itself is in group VI and has the formula of the hydrogen compound H2E.
Let’s find the molecular weight of H2E:
M (H2E) = M (H2) * 100 / w (H2) = 2 * 100 / 2.47 = 81 (amu).
Let’s find the atomic mass of E:
M (E) = M (H2E) – M (H2) = 81 – 2 = 79 (amu), which corresponds to the element selenium (Se), and the formula of the hydrogen compound is H2Se (hydrogen selenide).