Element X forms a higher oxide of composition X2O5. The hydrogen compound of this element is a gas

Element X forms a higher oxide of composition X2O5. The hydrogen compound of this element is a gas of composition XH3. The ratio of the molecular weights of the higher oxide to the hydrogen compound is 4.18. Show this element. Write the reaction equations: a) higher oxide of the element b) hydrogen compound of the element with potassium hydroxide

Given:
Х2О5 – higher oxide
ХН3 – hydrogen compound
Mr (X2O5): Mr (XH3) = 4.18

To find:
X -?

Decision:
1) Let Ar (X) = x;
2) Mr (X2O5) = Ar (X) * N (X) + Ar (O) * N (O) = x * 2 + 16 * 5 = (2x + 80);
3) Mr (XH3) = Ar (X) * N (X) + Ar (H) * N (H) = x * 1 + 1 * 3 = (x + 3);
4) Mr (X2O5): Mr (XH3) = 4.18;
(2x + 80) / (x + 3) = 4.18;
2x + 80 = 4.18x + 12.54;
2.18x = 67.46;
x = 30.945;
Ar (X) = x = 30.945 – phosphorus (P);
5) P2О5 + 6KOH => 2K3PO4 + 3H2O;
PH3 + 11KOH + 8KMnO4 => 8K2MnO4 + K3PO4 + 7H2O.

Answer: The unknown chemical element is phosphorus (P).