On heating anhydrous $Na_2CO_3$,........ is evolved.

Select the correct statement.

Which of the following substances is used as a fertilizer?

Green vitriol is . . . .

Select the incorrect order for the given properties:
$(a)$ $A_2B < AB < A_2B_3 = \text{Lattice Energy (L.E.)}$ (Charge of $B = -2$)
$(b)$ $Na_2CO_3 < K_2CO_3 < Rb_2CO_3 < Cs_2CO_3 = \text{Thermal stability}$
$(c)$ $MgF_2 < CaF_2 < SrF_2 < BaF_2 < BeF_2 = \text{Solubility}$
$(d)$ $LiOH < NaOH < KOH < RbOH < CsOH = \text{Solubility and stability}$

Choose the correct statement and mark the correct option given below:
$(a)$ $AgF$ is soluble and colourless in aqueous medium.
$(b)$ For $LiF$,solubility and melting point are both lower as compared to $NaF$.
$(c)$ Solubility of $Rb_2SO_4$ is less as compared to $BaSO_4$.
$(d)$ If $AgI$ is added to water,the colour of water will turn yellow from colourless.