In a nuclide,one $a.m.u.$ of mass is dissipated into energy to bind its nucleons. The energy equivalent of this mass is

$A$ compound $(A)$ is used in the preparation of washing soda to recover ammonia in the Solvay process. When $CO_2$ is bubbled through an aqueous solution of $(A)$,the solution turns milky. It is also used in whitewashing due to its disinfectant nature. What is the chemical formula of $(A)$?

The de-Broglie wavelength of an electron having $80 eV$ energy is nearly ($1 eV = 1.6 \times 10^{-19} J$,Mass of the electron $= 9 \times 10^{-31} kg$,Planck's constant $= 6.6 \times 10^{-34} J-s$) (in $text{ Å}$)

In the following figure,a body of mass $m$ is tied at one end of a light string and this string is wrapped around a solid cylinder of mass $M$ and radius $R$. At the moment $t = 0$,the system starts moving. If the friction is negligible,the angular velocity at time $t$ would be

$A$ metal $M$ which is not affected by strong acids like conc. $HNO_3$,conc. $H_2SO_4$ and conc. solutions of alkalies like $NaOH$,$KOH$ forms $MCl_3$ which finds use for toning in photography. The metal $M$ is

If $OA$ is equally inclined to $OX, OY$ and $OZ$ and if $A$ is $\sqrt{3}$ units from the origin,then $A$ is: