Which of the following does not produce $NO_2$ gas with concentrated $HNO_3$?

If a ladder weighing $250\,N$ is placed against a smooth vertical wall and the coefficient of friction between the ladder and the floor is $0.3$,what is the maximum force of friction available at the point of contact between the ladder and the floor?

$A$ body projected vertically upwards crosses a point twice in its journey at a height $h$ just after $t_1$ and $t_2$ seconds. Maximum height reached by the body is

Would you expect the second electron gain enthalpy of $O$ to be positive,more negative,or less negative than the first? Justify your answer.

One of the synthetic auxin is

Which is the best method to conserve the wild relatives of plants?