Pre class activity: Mole balances

Lecture notes for chemical reaction engineering

Solve the following problems

1. In the Decon process for the manufacture of chlorine, a dry mixture of hydrochloric acid gas and air is passed over a heated catalyst which promotes oxidation of acid. Air is used 30% in excess of that theoretically required. Calculate the weight of air·supplied per kilogram of the acid. (Atomic weight of chlorine = 35.5, Air contains 23.2% \ce{O2} by weight)

2. Chlorobenzene (\ce{C6H5Cl}) is nitrated using a mixture of nitric acid and sulphuric acid. During the pilot plant run, a charge consists of 100 kg of chlorobenzene, 106.5 kg of nitric acid of 65.5% strength, 108 kg of sulphuric acid of 93.6% strength. After two hours of operation, tbc final product mixture was analysed and found to contain 2% unreacted chlorobenzene. Also, the product distribution was found to be 66% paranitrocblorobenzene and 34% orthonitrochloro-benzene (by weight). The chemical reaction involved are:

   \begin{gathered} \ce{C6H5Cl} + \ce{HNO3} \rightarrow o \ce{C6H4ClNO2} + \ce{H2O} \\ \ce{C6H5Cl} + \ce{HNO3} \rightarrow p \ce{C6H4ClNO2} + \ce{H2O} \end{gathered}

   Calculate:

   1. analysis of charge,
   2. % conversion of chlorobenzene and
   3. composition of the product mixture. (Atomic weight data: H = 1, N = 14, S = 32, Cl = 35.5)

3. Pure sulphur is burnt in a sulphur burner with dry air. Oxygen is used 20% excess above that required for the complete combustion of sulphur lo \ce{SO3} The efficiency of burner is such that only 30% of the sulphur burns to \ce{SO3} and remainder goes to \ce{SO3}.

   Calculate:

   1. the analysis of the resulting mixture in mole% and
   2. the weight of gas per kg of sulphur burnt.