Which one of the following gives a sooty flame on combustion?

Which among the following is $NOT$ a feature of $S_N2$ mechanism?

If the pair of lines represented by $3 x^2 - 5 x y + P y^2 = 0$ and $6 x^2 - x y - 5 y^2 = 0$ have one line in common,then the sum of all possible values of $P$ is

If the normal to the parabola $y^2=4x$ at $P(1,2)$ meets the parabola again at $Q$,then the coordinates of $Q$ are

If $\Delta U$ and $\Delta W$ represent the increase in internal energy and work done by the system respectively in a thermodynamic process,which of the following is true?

Which of the following substances is obtained from the fungus $Claviceps$ $\text{purpurea}$ (ergot)?