31. (a) (i) Account for the following : (I) $\text{MnO}$ is basic while $\text{Mn}_2\text{O}_7$ is acidic. (II) Iron has higher enthalpy of atomization than that of copper. (III) $\text{Mn}^{3+}$ is a stronger oxidising agent than $\text{Cr}^{3+}$. (ii) How do you prepare potassium dichromate from sodium chromate ? Write balanced chemical equation for each step. OR (b) Answer the following questions : (i) Why is chemistry of actinoids more complicated as compared to lanthanoids ? (ii) $E^\circ_{\text{M}^{2+}/\text{M}}$ values are not regular for first row transition elements ($3\text{d}$ series). Why ? (iii) Identify the following : (I) Oxoanion of chromium which is stable in acidic medium. (II) The lanthanoid element that exhibits $+4$ oxidation state. (iv) Write the products obtained on heating $\text{KMnO}_4$. (v) Predict which of the following ions will be coloured in aqueous solution : $\text{Cu}^+, \text{Sc}^{3+}, \text{Fe}^{2+}, \text{Ti}^{3+}, \text{Zn}^{2+}$

Year	Paper Code	Set	Position
CBSE 2026	Series 56-4	Set 1	Question 31
CBSE 2026	Series 56-4	Set 2	Question 32
CBSE 2026	Series 56-4	Set 3	Question 33

• Step 1: Stating the fundamental formula / law statement (+1 Mark)
• Step 2: Intermediate mathematical substitution or proof steps (+1 Mark)
• Step 3: Correct final value or conclusion with mandatory SI units (+1 Mark)