If the number average molecular weight and weight average molecular weight of a polymer are $40000$ and $60000$ respectively,the polydispersity index of the polymer will be

Find the oxidation state of sodium in $Na_{2}O_{2}$.

The equation $8 x^2-24 x y+18 y^2-6 x+9 y-5=0$ represents a

The electrons which take part in order to exhibit variable oxidation states by transition metals are

The pole of the straight line $x+4y=4$ with respect to the ellipse $x^2+4y^2=4$ is

The figure shows the variation of the gravitational acceleration $a_g$ of four planets with the radial distance $r$ from the centre of the planet for $r \geq$ radius of the planet. Plots $1$ and $2$ coincide for $r \geq R_2$,and plots $3$ and $4$ coincide for $r \geq R_4$. The sequence of the planets in the descending order of their densities is: