Which of the following compounds is consumed during the preparation of $Na_2CO_3$ by Solvay's process?

How many stereoisomers are possible for the following molecule?

The frequency of vibration in a vibration magnetometer of the combination of two bar magnets of magnetic moments $M_1$ and $M_2$ is $6 ~Hz$ when like poles are tied together and it is $2 ~Hz$ when the unlike poles are tied together,then the ratio $M_1: M_2$ is

If the function $f(x) = 2x^3 - 9ax^2 + 12a^2x + 1$,where $a > 0$,attains its maximum and minimum values at $p$ and $q$ respectively,such that $p^2 = q$,then what is the value of $a$?

Two fair dice are rolled. The probability of the sum of digits on their faces being greater than or equal to $10$ is

If $f: R \rightarrow R$ and $g: R \rightarrow R$ are defined by $f(x)=|x|$ and $g(x)=[x-3]$ for $x \in R$,then $\{g(f(x)):-\frac{8}{5} < x < \frac{8}{5}\}$ is equal to