Pyrosulphuric acid is oleum. It is obtained when sulphur trioxide gas is passed through conc H₂SO₄ solution.

$$\begin{gathered} {\mathrm{H}}_2{\mathrm{SO}}_4 + {\mathrm{SO}}_3 \to {\mathrm{H}}_2{\mathrm{SO}}_2{\mathrm{O}}_7 \\ 98\% \mathrm{oleum}( \mathrm{or} \mathrm{pyrosulphuric} \mathrm{acid}) \end{gathered}$$

 The structure of pyrosulphric acid is

When colourless HI is added to pyrosulphuric acid, its colour becomes violet because pyrosulphuric acid oxidises I^- to I₂.

$$\begin{gathered} {\mathrm{H}}_2{\mathrm{SO}}_4 + 2\mathrm{HI} \to 2{\mathrm{H}}_2\mathrm{O} + {\mathrm{SO}}_2 + {\mathrm{I}}_2 \\ \mathrm{colourless} \mathrm{violet} \end{gathered}$$

Since the organic compound 'A' reduces ammoniacal silver nitrate (Tollen's reagent), it must be an aldehyde. Moreover, with Brady's reagent (2, 4-dinitro phenyl hydrazine) it gives a precipitate of molecular formula C₉H₁₀N₄O₄ it must be propanal (CH₃CH₂CHO). The reactions are as follows

When NH₃ and CO₂ are directly introduced into a gypsum slurry, ammonium sulphate is obtained. This method is called continental engineering process.

$$\begin{gathered} 2{\mathrm{NH}}_3 + {\mathrm{CaSO}}_4·2{\mathrm{H}}_2\mathrm{O} + {\mathrm{CO}}_2 \to ({\mathrm{NH}}_4{)}_2{\mathrm{SO}}_4 + {\mathrm{CaCO}}_3 \\ \mathrm{gypsum} \end{gathered}$$

CaCO₃ is the byproduct of the reaction.

Given, pH = 10

[H⁺] = 1 x 10^-10 mol/L

  Number of H⁺ ions in 1 L of solution
= 6.023 10²³ 1 X 10^-10
= 6.023 x 10¹³
  Number of H⁺ ions in 1 mL of solution
= 6.023 X 10¹³ X 10^-3
= 6.023 X 10¹⁰