What are the substances which mimic the natural chemical messengers?

The lowest $O-O$ bond length in the following molecules is:

Vitellogenesis occurs during the formation of

When $KMnO_4$ solution is added to hot oxalic acid solution,the decolourisation is slow in the beginning but becomes instantaneous after some time. This is because

$A$ ball of mass $160\, g$ is thrown up at an angle of $60^\circ$ to the horizontal at a speed of $10\, m\,s^{-1}$. The angular momentum of the ball at the highest point of the trajectory with respect to the point from which the ball is thrown is nearly ........ $kg\, m^2/s$ $(g = 10\, m\,s^{-2})$.

Degenerate electron pressure will not be sufficient to prevent core collapse of a white dwarf if its mass becomes $n$ times the solar mass. The value of $n$ is: