Which of the following is most basic in nature?

When a chromite ore $(A)$ is fused with sodium carbonate in free excess of air and the product is dissolved in water,a yellow solution of compound $(B)$ is obtained. After treatment of this yellow solution with sulphuric acid,compound $(C)$ can be crystallised from the solution. When compound $(C)$ is treated with $KCl$,orange crystals of compound $(D)$ crystallise out. Identify $A$ to $D$ and also explain the reactions.

In ruby and emerald,the metal ion$(s)$ present is/are

Correct statement for $CeO_2$ is/are:
$1$. It is diamagnetic in nature.
$2$. It is a good oxidising agent.
$3$. It is a colourless compound.

Iodine is formed when potassium iodide reacts with a solution of

Consider the following reactions:
$NaCl + K_{2}Cr_{2}O_{7} + H_{2}SO_{4}$ (conc.) $\rightarrow (A) +$ side products
$(A) + NaOH \rightarrow (B) +$ side product
$(B) + H_{2}SO_{4}$ (dilute) $+ H_{2}O_{2} \rightarrow (C) +$ side product
The sum of the total number of atoms in one molecule each of $(A)$,$(B)$,and $(C)$ is: