The major product obtained on interaction of phenol with sodium hydroxide and carbon dioxide is

The major product of the following reaction is:

$A$ sulphide ore is first converted into its oxide before reduction. This is done because

If the sum of any two roots of the equation $x^3+p x^2+q x+r=0$ is zero,then

$Fe$ is made passive by

$A$ launching vehicle carrying an artificial satellite of mass $m$ is set for launch on the surface of the earth of mass $M$ and radius $R$. If the satellite is intended to move in a circular orbit of radius $7R$,the minimum energy required to be spent by the launching vehicle on the satellite is (Gravitational constant $= G$)