Step 1: Write the molecular formulae of the acids.
Peroxysulphuric acid (also known as Caro's acid) has the molecular formula: \[ \mathrm{H_2S_2O_8} \] It contains 8 oxygen atoms. Pyrosulphuric acid (also known as oleum) has the molecular formula: \[ \mathrm{H_2S_2O_7} \] It contains 7 oxygen atoms.
Step 2: Add the total number of oxygen atoms.
\[ 8 \text{ (from } \mathrm{H_2S_2O_8}) + 7 \text{ (from } \mathrm{H_2S_2O_7}) = 15 \]
Consider the following two reactions A and B: 
The numerical value of [molar mass of $x$ + molar mass of $y$] is ___.
Which one of the following graphs accurately represents the plot of partial pressure of CS₂ vs its mole fraction in a mixture of acetone and CS₂ at constant temperature?

Consider the following reaction sequence: 
Given: Compound (x) has percentage composition \(76.6%\ \text{C}\), \(6.38%\ \text{H}\) and vapour density \(=47\). Compound (y) develops a characteristic colour with neutral \(\mathrm{FeCl_3}\) solution. Identify the {INCORRECT statement.}