Iron may be rendered passive by treatment with a concentrated solution of

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:

Iron becomes passive by ..................... due to formation of .....................

Which of the following is the correct order of acidic character?

Transition metals vary widely in their chemical reactivity. Explain this with examples or write about the reactivity of $3d$ series metals with acids.

Select the incorrect statement.