In $\text{CrO}_5$, the central chromium atom is bonded to one oxygen atom via a double bond (oxide linkage) and four oxygen atoms via single bonds forming two peroxide linkages (–O–O–). Let the oxidation state of $\text{Cr}$ be $x$. The oxidation state of oxygen in an oxide linkage is $-2$ . The oxidation state of oxygen in a peroxide linkage is $-1$ . So, the sum of oxidation states is: $x + 1(-2) + 4(-1) = 0 \implies x - 6 = 0 \implies x = +6$. Thus, the oxidation state of $\text{Cr}$ in $\text{CrO}_5$ is $+6$.