$Cu^{2+}(aq.) + X^{-}(aq.) \xrightarrow{R.T.} CuX \downarrow + X_2$
$X$ cannot be

How many ions liberate $H_2$ gas with dilute acids among the given species:
$Mn^{2+}, Cr^{3+}, Cr^{2+}, Zn^{2+}, Cu^{2+}, Sc^{3+}, Hg^{2+}$

Four successive members of the first row transition elements are listed below with their atomic numbers. Which of these elements has the maximum $E^o_{M^{3+}/M^{2+}}$ value?

Which of the following statements is not correct?

The compound $AgF_2$ is an unstable compound. However,if formed,the compound acts as a very strong oxidizing agent. Why?

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