Which of the following complex ions exhibits optical isomerism? ($en = 1,2$-diaminoethane)

$A$ meter bridge is set up as shown to determine end corrections at $A$ and $B$. When a resistance of $15 \ \Omega$ is used in the left gap and $20 \ \Omega$ in the right gap,the null point is obtained at a distance of $42 \ cm$ from $A$. When these resistances are interchanged,the null point is obtained at a distance of $57 \ cm$ from $A$. The values of the end corrections are:

If the equation of the locus of a point equidistant from the points $(a_1, b_1)$ and $(a_2, b_2)$ is $(a_1 - a_2)x + (b_1 - b_2)y + c = 0$,then the value of $c$ is

Compound $A$ $(C_3H_6O)$ undergoes the following reactions to form $B$ and $C$. Identify $A$,$B$,and $C$.

The $P-V$ diagram of a diatomic gas is a straight line passing through the origin. The molar heat capacity of the gas in this process will be:

The de-Broglie wavelength of the electron in the ground state of the hydrogen atom is . . . . . . $\mathring{A}$ (radius of the first orbit of hydrogen atom $= 0.53 \ \mathring{A}$).