Which of the following gases present in the air darkens the surface painted with white lead?

From the ground state electronic configuration of the elements given below,pick the one with the highest value of second ionisation energy.

The equation of the circle passing through the point $(1,2)$ and through the points of intersection of $x^2+y^2-4x-6y-21=0$ and $3x+4y+5=0$ is given by

The diagram of a logic circuit is given below. The output $F$ of the circuit is represented by

$3.65 \ g$ of $HCl$ is dissolved in $16.2 \ g$ of water. The mole fraction of $HCl$ in the resulting solution is

Power supplied to a particle of mass $2\,kg$ varies with time as $P = \frac{3t^2}{2}\,W$. Here $t$ is in seconds. If the velocity of the particle at $t = 0$ is $v = 0$,the velocity of the particle at time $t = 2\,s$ will be .............. $m/s$.