Which elements are present in the $s$-block?

For a good quality cement,the ratio of lime to the total of the oxides of $Si$,$Al$ and $Fe$ should be as close as to :

The pair$(s)$ of reagents that yield paramagnetic species is/are:
$A$. $Na$ and excess of $NH_3$
$B$. $K$ and excess of $O_2$
$C$. $Cu$ and dilute $HNO_3$
$D$. $O_2$ and $2-ethylanthraquinol$

The correct solubility order is/are:
$I. CaCO_3 > SrCO_3 > BaCO_3$
$II. Li_2CO_3 < Na_2CO_3 < K_2CO_3$
$III. K_2CO_3 < Rb_2CO_3 < Cs_2CO_3$
$IV. Na_2CO_3 > K_2CO_3 > Rb_2CO_3$

What is the nature of metal nitrates?

Match the following compounds with their respective uses:

Compound	Uses
$1. CaCO_3$	$a.$ In purification of coal gas
$2. Ca(OH)_2$	$b.$ As an antacid
$3. CaO$	$c.$ In paper and textile industries
$4. Na_2CO_3 \cdot 10H_2O$	$d.$ In glass and leather industries