NEET Practice Questions (MCQs) with Answers & Solutions

Joseph Priestley is credited with the discovery of oxygen in 1774. He conducted experiments that involved heating mercuric oxide and collecting the gas it released, which was later identified as oxygen. Although Carl Wilhelm Scheele also discovered oxygen independently around the same time, Priestley's findings were published first.

The shape of $O_2F_2$ (dioxygen difluoride) is similar to that of $H_2O_2$ (hydrogen peroxide). Both molecules have a non-linear (bent) structure due to the presence of lone pairs of electrons on the oxygen atoms, leading to a skewed or twisted shape.

Chalcogens are elements in Group 16 of the periodic table, which include oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and polonium (Po). Sodium (Na) is an alkali metal and not a chalcogen.

A suboxide is a type of oxide where the ratio of the element to oxygen is lower than in normal oxides. $C_3O_2$ (carbon suboxide) is a well-known suboxide where the carbon to oxygen ratio is less than in normal carbon oxides like $CO$ and $CO_2$. Therefore, $C_3O_2$ is the correct answer.

Potassium superoxide ($KO_2$) reacts with carbon dioxide ($CO_2$) to produce potassium carbonate ($K_2CO_3$) and oxygen ($O_2$) gas. The reaction is as follows: $4KO_2 + 2CO_2 ightarrow 2K_2CO_3 + 3O_2$. Thus, the gas produced in this reaction is $O_2$.

$H_2SO_4$ acts as a dehydrating agent by removing water from other compounds. When it reacts with oxalic acid ($H_2C_2O_4$), it dehydrates it to form carbon monoxide ($CO$), carbon dioxide ($CO_2$), and water ($H_2O$). The reaction is: $H_2C_2O_4 ightarrow CO + CO_2 + H_2O$ in the presence of $H_2SO_4$. Therefore, the correct answer is $H_2C_2O_4$.

Dithionic acid has the molecular formula H₂S₂O₆. It consists of two sulfur atoms, six oxygen atoms, and two hydrogen atoms. The other given options do not match the correct formula for dithionic acid.

The \alpha and \beta forms of sulphur are allotropes that are stable at 369 K. This temperature corresponds to the transition point between these two forms. At this temperature, both allotropes can coexist in equilibrium.