Phosphorus pentachloride in the solid state exists as:

When $H_2SO_4$ reacts with $PCl_5$,the obtained product is/are:

What is the hybridization state of the central atom in the conjugate base of $NH_4^{+}$ ion?

$A$ pair of perpendicular straight lines passes through the origin and also through the point of intersection of the curve $x^2+y^2=4$ with $x+y=a$. The set containing the value of $a$ is

$A$ and $B$ are two metallic rings placed at opposite sides of an infinitely long straight conducting wire as shown. If the current in the wire is slowly decreased,the direction of the induced current will be:

$A$ segment of wire vibrates with a fundamental frequency of $450 ~Hz$ under a tension of $9 ~kg-wt$. The tension at which the fundamental frequency of the same wire becomes $900 ~Hz$ is