The highest oxide of a chemical element of group V has a formula weight of 142.

The highest oxide of a chemical element of group V has a formula weight of 142. Name the chemical element, make the formula of the oxide and the corresponding acid.

Let’s compose the general formula for this oxide:
E2O5
Let us denote the atomic mass of the element E as x.
Then, the molar mass of the oxide will be 2x + 16 * 5 = 2x + 80 or 142
Let’s make the equation:
2x + 80 = 142
2x = 62
x = 31
We look at the periodic table and see that an element with an atomic mass of 31 is phosphorus
This means that the formula of its oxide is P2O5, and the corresponding acid has the formula H3PO4