Which of the following substances is used as a fertilizer?

Which of the following electronic configurations belongs to $s-$block elements?

Which of the following compounds is useful as a fertilizer?

An aqueous solution of a colourless metal sulphate $M$ gives a white precipitate with $NaOH$. This precipitate is soluble in excess of $NaOH$. On passing $H_2S$ through this solution,a white precipitate is formed. The metal $M$ in the salt is:

$A$ mixture of sodium oxide and calcium oxide is dissolved in water and saturated with excess carbon dioxide gas. The resulting solution is ...... It contains ......... :

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 :