The ${E^0}_{M^{3+}/M^{2+}}$ values for $Cr, Mn, Fe$ and $Co$ are $-0.41, +1.57, +0.77$ and $+1.97 \ V$ respectively. For which one of these metals is the change in oxidation state from $+2$ to $+3$ the easiest?

Arrange the oxides $CrO$,$CrO_3$,and $Cr_2O_3$ in the decreasing order of acidic strength.

Given below are two statements for catalytic properties of transition metals. Statement $I$: First row transition metals which act as catalyst utilise their $3d$ electrons only for formation of bonds between reactant molecules and atoms on the surface of catalyst. Statement $II$: There is increase in the concentration of reactants on the surface of catalyst which strengthens the bonds in reacting molecules. In the light of the above statements, choose the correct answer from the options given below:

Which one of the following oxides is ionic?

Identify the basic oxide from the following:

Which of the following statements are correct?
$A$. The $M^{3+}/M^{2+}$ reduction potential for iron is greater than manganese.
$B$. The higher oxidation states of first row $d$-block elements get stabilized by oxide ion.
$C$. Aqueous solution of $Cr^{2+}$ can liberate hydrogen from dilute acid.
$D$. Magnetic moment of $V^{2+}$ is observed between $4.4-5.2 \ BM$.
Choose the correct answer from the options given below: