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

Consider a reaction $A+R \rightarrow$ Product. The rate of this reaction is measured to be $k[A][R]$. At the start of the reaction, the concentration of $R,[R]_0$, is $10-$times the concentration of $A,[A]_0$. The reaction can be considered to be a pseudo first order reaction with assumption that $k[R]=k^{\prime}$ is constant. Due to this assumption, the relative error $(in \%)$ in the rate when this reaction is $40 \%$ complete, is $....$
$[ k$ and $k^{\prime}$ represent corresponding rate constants$]$

If the plane $3x - 2y - z - 18 = 0$ meets the coordinate axes at $A$, $B$, and $C$, then the centroid of $\triangle ABC$ is:

If the parametric equations of the circle passing through the points $(3,4), (3,2)$ and $(1,4)$ are $x=a+r \cos \theta$ and $y=b+r \sin \theta$,then find the value of $b^a r^a$.

$A$ Young's double slit experiment uses a monochromatic source. The shape of the interference fringes formed on a screen is

Which of the following is $NOT$ obtained when a mixture of methyl bromide and ethyl bromide is treated with sodium metal in the presence of dry ether?