The nature of oxides $V_{2}O_{3}$ and $CrO$ is indexed as '$X$' and '$Y$' type respectively. The correct set of $X$ and $Y$ is:

The electronic configuration of $Cu(II)$ is $3d^9$ whereas that of $Cu(I)$ is $3d^{10}$. Which of the following is correct?

Which of the following ions can reduce dilute acid to give hydrogen gas?

The incorrect statement$(s)$ among $(a)-(c)$ is (are) :-
$(a)$ $W(VI)$ is more stable than $Cr(VI)$
$(b)$ In the presence of $HCl$,permanganate titrations provide satisfactory results.
$(c)$ Some lanthanoid oxides can be used as phosphors.

Addition of high proportions of manganese makes steel useful in making rails of railroads,because manganese

Highest oxidation state of manganese in fluoride is $+4$ $(MnF_4)$ but highest oxidation state in oxides is $+7$ $(Mn_2O_7)$ because $..........$