Prolonged heating is avoided during the preparation of ferrous ammonium sulphate to:

Which of the following chemicals may be used to identify three unlabelled beakers containing conc. $NaOH$,conc. $H_{2}SO_{4}$ and water?

Match Column-$I$ and Column-$II$ with the correct relation:

Column-$I$	Column-$II$
$(i)$ Ammonium phosphomolybdate	$(a)$ $(NH_4)_2MoO_4$
$(ii)$ Ammonium phosphate	$(b)$ $Mg^{2+} + NH_4OH$
$(iii)$ Mixture of magnesia	$(c)$ $H_3PO_4$
$(iv)$ Ammonium molybdate	$(d)$ $(NH_4)_3PO_4$
$(v)$ Phosphoric acid	$(e)$ $(NH_4)_3PO_4 \cdot 12MoO_3$

For the kinetic study of the reaction of iodide ion with $H_{2}O_{2}$ at room temperature, which of the following statements are correct?
$(A)$ Always use freshly prepared starch solution.
$(B)$ Always keep the concentration of sodium thiosulphate solution less than that of $KI$ solution.
$(C)$ Record the time immediately after the appearance of blue colour.
$(D)$ Record the time immediately before the appearance of blue colour.
$(E)$ Always keep the concentration of sodium thiosulphate solution more than that of $KI$ solution.
Choose the correct answer from the options given below:

The number of white coloured salts among the following is .................
$A$. $SrSO_4$ $B$. $Mg(NH_4)PO_4$ $C$. $BaCrO_4$ $D$. $Mn(OH)_2$ $E$. $PbSO_4$ $F$. $PbCrO_4$ $G$. $AgBr$ $H$. $PbI_2$ $I$. $CaC_2O_4$ $J$. $[Fe(OH)_2(CH_3COO)]$

$CaCO_3$ (aqueous suspension) $\xrightarrow{AcOH}$ $\xrightarrow{Na_2C_2O_4 \text{ solution}}$
Which of the following observations is correct for the above experiment?