Sulphuric Acid and Nitric Acid Manufacture Questions and Answers

Answer: A

Sulphur is burned to the dioxide, which is then oxidised over a catalyst and absorbed. The oxidation step is the one that needed a catalyst and gave the process its name. Sulphur and air are the only raw materials needed.

Answer: B

Vanadium replaced platinum because it is far cheaper and much less easily poisoned by arsenic. Iron oxide belongs to ammonia synthesis and nickel to hydrogenation duties. Platinum was used in the earliest contact plants.

Answer: C

Both are true and the reason gives the two advantages: gas purification is still required, but the tolerance of the vanadium catalyst makes the process much less fragile than the platinum one was. Feed gas is still cleaned before the converter.

Answer: D

The first two are correct. The third is wrong, because three moles become two, which is why raised pressure would favour conversion although in practice the process runs near atmospheric pressure. Compression would cost more than it returns here.

Answer: A

Each bed converts a portion and heats the gas, and cooling before the next bed restores a favourable equilibrium. Four beds are typical and take the conversion above ninety-eight per cent. Each bed operates on the same catalyst.

Answer: B

Both are true and the reason gives the principle: each bed is allowed to approach equilibrium and then the gas is cooled so that a further approach becomes possible, which is the standard treatment for a reversible exothermic reaction.

Answer: C

Correct answer: absorption in water forms a persistent mist

Sulphur trioxide meeting water vapour forms sulphuric acid in the gas phase as an extremely fine mist, which passes straight through an absorption tower and is very difficult to collect. Absorbing into 98 per cent acid instead keeps the water activity low so the reaction happens in the liquid, and the acid produced is diluted back to 98 with a controlled water addition.

Answer: D

Water absorption produces an acid mist that will not coalesce, so strong sulphuric acid is used as the absorbing medium with water added separately to maintain its strength. This is one of the more counter-intuitive features of the process.

Answer: A

It is also called fuming sulphuric acid and is used where a water-free sulphonating agent is needed. Diluting it with water gives sulphuric acid of any strength up to a hundred per cent. It is shipped as a convenient form of the trioxide.

Answer: B

The four vessels appear in every flowsheet of the process, and the drying tower is the one most often forgotten although moisture in the air would cause mist in the absorber later. Each vessel appears on every flowsheet of the process.