Question

Sulfur trioxide, is what will fume in air?
(A) Black crystalline solid
(B) Red crystalline solid
(C) Colourless to white crystalline solid
(D) Colourless gas

Answer 1

Hint : The chemical compound sulphur trioxide has the formula $S{O_3}$ . Sulfur oxide has been called "unquestionably the most significant commercially." As a precursor to sulfuric acid, it is manufactured on a large scale. Sulfur trioxide comes in a variety of forms, including a gaseous monomer, a crystalline trimmer, and a solid polymer. Sulfur trioxide is a solid with a narrow liquid range at slightly below room temperature. Acid rain is mostly caused by gaseous $S{O_3}$ .

Complete Step By Step Answer:
$S{O_3}$ is a trigonal planar molecule. Its structure belongs to the ${D_3}h$ point group, as predicted by VSEPR theory. The sulphur atom has a formal charge of 0 and an oxidation state of +6. With all three S-O bond lengths identical at 1.42, the S-O bonding is delocalized. Gaseous sulphur trioxide has no electrical dipole moment. The contact technique is used to produce $S{O_3}$ in industry. Sulfur dioxide is created when sulphur or iron pyrite is burned. After being cleaned by electrostatic precipitation, the $S{O_2}$ is oxidised by ambient oxygen over a catalyst at temperatures ranging from 400 to 600 degrees Celsius. On a kieselguhr or silica substrate, a typical catalyst consists of vanadium pentoxide ($V_2O_5$) activated with potassium oxide ${K_2}O$ . Platinum is also quite useful, but it is too costly and is poisoned (made useless) by impurities much more quickly. Sulfur trioxide is mostly transformed into sulfuric acid in this method. Sulfur trioxide is a colourless to white crystalline substance that fumes in the presence of oxygen. When $S{O_3}$ is exposed to air, it burns.
Hence option C is correct.

Note :
In sulfonation processes, sulphur trioxide is used as a reagent. Detergents, dyes, and medications are all made possible by these procedures. Sulfur trioxide is either produced in situ or utilised as a solution in sulfuric acid. The vapour pressure of liquid sulphur trioxide is the same as that of the gamma form.