NEET 2015 Code A - Mock Test

$2,3$ -Dimethyl-$2$ -butene can be prepared by heating which of the following compounds with a strong acid?

Gadolinium belongs to the $4f$ series. Its atomic number is $64$. Which of the following is the correct electronic configuration of gadolinium?

The formation of the oxide ion, ${\text{O}}^{2-}(g)$, from oxygen atom requires first an exothermic and then an endothermic step as shown below:$\text{O}(g)+e^{-}⟶{\text{O}}^{-}(g);{\Delta }_f{H}^{\ominus }=-141{\text{kJ mol}}^{-1}$${\text{O}}^{-}(g)+e^{-}⟶{\text{O}}^{2-}(g);{\Delta }_f{H}^{\ominus }=+780{\text{kJ mol}}^{-1}$ Thus the process of formation of ${\text{O}}^{2-}$ in gas phase is unfavourable though ${\text{O}}^{2-}$ is isoelectronic with neon. It is due to the fact that:

The number of structural isomers possible from the molecular formula ${\text{C}}_3{\text{H}}_9\text{N}$ is:

If the equilibrium constant for ${\text{N}}_2(g)+{\text{O}}_2(g)\rightleftharpoons 2\text{NO}(g)$ is $K$, the equilibrium constant for $\frac{1}{2}{\text{N}}_2(g)+\frac{1}{2}{\text{O}}_2(g)\rightleftharpoons \text{NO}(g)$ will be: