Reactant A converts to product D through the given mechanism (with the net evolution of heat):

A → B     slow;     ΔH = +ve

B → C     fast;     ΔH = -ve

C → D     fast;     ΔH = -ve

Which of the following represents the above reaction mechanism?

Formation of $\mathrm{Na}_4\left[\mathrm{Fe}(\mathrm{CN})_5 \mathrm{NOS}\right]$, a purple coloured complex formed by addition of sodium nitroprusside in sodium carbonate extract of salt indicates the presence of :

Consider the following reactions. From these reactions which reaction will give carboxylic acid as a major product ?

(A) $\quad \mathrm{R}-\mathrm{C} \equiv \mathrm{N} \xrightarrow[\text { mild condition }]{\text { (i) } \stackrel{+}{\mathrm{H}} / \mathrm{H}_2 \mathrm{O}}$

(B) $\quad \mathrm{R}-\mathrm{MgX} \xrightarrow[\text { (ii) } \mathrm{H}_3 \mathrm{O}^{+}]{\text {(i) } \mathrm{CO}_2}$

(C) $\mathrm{R}-\mathrm{C} \equiv \mathrm{N} \xrightarrow[\text { (ii) } \mathrm{H}_3 \mathrm{O}^{+}]{\text {(i) } \mathrm{SnCl}_2 / \mathrm{HCl}}$

(D) $\quad \mathrm{R} \cdot \mathrm{CH}_2 \cdot \mathrm{OH} \xrightarrow{\mathrm{PCC}}$

(E)

Choose the correct answer from the options given below :

The nature of oxide $\left(\mathrm{TeO}_2\right)$ and hydride $\left(\mathrm{TeH}_2\right)$ formed by Te , respectively are :