Which of the following statements is true for an $N$-type semiconductor?

The pair of compounds,which cannot exist together in a solution is

In which of the following is the hydration energy higher than the lattice energy?

The condition that $f(x)=a x^3+b x^2+c x+d$ has no extreme value,is

Two particles of equal mass have velocities $\overrightarrow{v}_1=4 \hat{i} \text{ ms}^{-1}$ and $\overrightarrow{v}_2=4 \hat{j} \text{ ms}^{-1}$. The first particle has an acceleration $\overrightarrow{a}_1=(5 \hat{i}+5 \hat{j}) \text{ ms}^{-2}$ while the acceleration of the other particle is zero. The centre of mass of the two particles moves in a path of

Which reaction involves a change in the electron pair geometry for the underlined atom?