Explain with neat suitable diagram determination of Carbon and hydrogen by ultimate analysis

Principle: a known mass of coal is burnt completely in a current of dry, CO₂-free oxygen. Its carbon becomes CO₂ and its hydrogen becomes H₂O.

\( \mathrm{C + O_2 \rightarrow CO_2}; \quad \mathrm{H_2 + \tfrac12 O_2 \rightarrow H_2O} \)

The H₂O is absorbed in a weighed U-tube of anhydrous CaCl₂, and the CO₂ in a weighed KOH bulb.

\( \mathrm{CaCl_2 + 7H_2O \rightarrow CaCl_2\cdot 7H_2O}; \quad \mathrm{2KOH + CO_2 \rightarrow K_2CO_3 + H_2O} \)

 O2 --> [ combustion tube with coal in boat, heated furnace (CuO) ] --> [CaCl2 U-tube] --> [KOH bulbs] --> exit
 (dry,                                                                   absorbs H2O        absorbs CO2
  CO2-free)

Procedure: about 1–2 g of accurately weighed coal is placed in a boat inside the combustion tube and burnt in O₂. The gases pass over hot CuO, which ensures complete oxidation. The increase in weight of the CaCl₂ tube gives the mass of H₂O, and the increase in weight of the KOH bulbs gives the mass of CO₂.

Calculation (W = mass of coal, x = increase in weight of the KOH tube, y = increase in weight of the CaCl₂ tube):

\( \%C = \dfrac{x \times 12 \times 100}{44 \times W} \) (44 g of CO₂ contains 12 g of C)

\( \%H = \dfrac{y \times 2 \times 100}{18 \times W} \) (18 g of H₂O contains 2 g of H)

Significance: the higher the %C, the higher the calorific value and the better the coal. Hydrogen raises the calorific value, but most of it is present as moisture or volatile matter.