Which of the following is $NOT$ produced by the reaction of ethanol with $H_2SO_4$?

$A$ potentiometer wire of length $1\,m$ is connected in series with a resistance of $490\,\Omega$ and a battery of $2\,V$. If the potential gradient is $0.2\,mV/cm$,then the resistance of the potentiometer wire is ............$\Omega$. (in $.9$)

The figure shows a transparent sphere of radius $R$ and refractive index $\mu$. An object $O$ is placed at a distance $x$ from the pole of the first surface so that a real image is formed at the pole of the exactly opposite surface. If $x = \infty$,then the value of $\mu$ is

The molecular interactions responsible for hydrogen bonding in $HF$ are:

What is the maximum number of rectangular components into which a vector can be split in space?

If $(a \times b)^2 + (a \cdot b)^2 = 144$ and $|a| = 4$,then $|b| = $