Problem:
An aromatic hydrocarbon with empirical formula C5H4 on treatment with concentrated H2SO4 gives a mono sulfonic acid. 0.104 gram of the acid required 10 ml of N/20 NAOH for complete neutralization. Determine the molecular formula of the hydrocarbon.

Solution:

Step 1: Determining the empirical formula
The empirical formula represents the simplest ratio of atoms in a compound. In this case, the empirical formula is given as C5H4.

Step 2: Determining the molar mass of the mono sulfonic acid
To determine the molecular formula, we need to find the molar mass of the mono sulfonic acid. We are given that 0.104 grams of the acid required 10 ml of N/20 NAOH for complete neutralization.

The molar mass of NAOH is 22.99 + 16 + 1 = 39.99 g/mol.
The molar concentration of NAOH is N/20, which means 1 liter of the solution contains N/20 moles of NAOH.

Using the equation:
Moles of NAOH = Volume of NAOH solution (in liters) * Molar concentration of NAOH

Moles of NAOH = 10 ml * (1/1000) L/ml * (1/20) mol/L = 0.0005 mol

Since 1 mole of NAOH reacts with 1 mole of mono sulfonic acid, the moles of mono sulfonic acid can be determined as 0.0005 mol.

The mass of the mono sulfonic acid can be calculated using its molar mass:
Mass of mono sulfonic acid = Moles of mono sulfonic acid * Molar mass of mono sulfonic acid

Mass of mono sulfonic acid = 0.0005 mol * Molar mass of mono sulfonic acid

Step 3: Determining the molecular formula
To determine the molecular formula, we need to find the molar mass of the hydrocarbon and compare it with the mass of the mono sulfonic acid.

The molar mass of carbon (C) is 12.01 g/mol, and the molar mass of hydrogen (H) is 1.01 g/mol.

Since the empirical formula is C5H4, the molar mass of the empirical formula is:
Molar mass of empirical formula = (5 * Molar mass of carbon) + (4 * Molar mass of hydrogen)

Molar mass of empirical formula = (5 * 12.01) + (4 * 1.01) = 60.05 g/mol

If the molar mass of the hydrocarbon is a multiple of the molar mass of the empirical formula, then the molecular formula is a multiple of the empirical formula.

Molar mass of hydrocarbon = n * Molar mass of empirical formula

By comparing the mass of the mono sulfonic acid with the calculated molar mass of the hydrocarbon, we can determine the value of n.

Molar mass of hydrocarbon = Mass of mono sulfonic acid

n * Molar mass of empirical formula = 0.0005 mol * Molar mass of mono sulfonic acid

n * 60.05 g/mol = 0.0005 mol

C15 h12