The property of hydrogen which distinguishes it from alkali metals is

What is the percentage of lead in a lead pencil (in $\%$)?

In an $FM$ system, a $7\, kHz$ signal modulates a $108\, MHz$ carrier such that the frequency deviation is $50\, kHz$. The carrier swing is: (in $ kHz$)

How many numbers greater than $24000$ can be formed by using digits $1, 2, 3, 4, 5$ when no digit is repeated?

$A$ particle performs linear $SHM$. At a particular instant,the velocity of the particle is $u$ and acceleration is $\alpha$ (both having the same direction). At another instant,the velocity is $v$ and acceleration is $\beta$ $(0 < \alpha < \beta)$ (both in opposite directions to each other). The distance between the two positions is

In the following reaction,$A$ and $B$ respectively are:
$A$ $\xrightarrow{HBr} C_2H_5Br$ $\xrightarrow{B} A$