Chemistry MCQs for NEET — Practice Questions with Answers

In the given reaction, $2Al + Cr_2O_3 ightarrow Al_2O_3 + 2Cr$, aluminum (Al) is oxidized. Oxidation refers to the loss of electrons. Here, aluminum changes from an oxidation state of 0 in $2Al$ to +3 in $Al_2O_3$. Thus, Al is the substance that gets oxidized.

The reducing agent is the substance that donates electrons and gets oxidized in the process. In the reaction $2Al + Cr_2O_3 ightarrow Al_2O_3 + 2Cr$, aluminum (Al) donates electrons to reduce $Cr_2O_3$ to Cr and itself gets oxidized to $Al_2O_3$. Therefore, Al is the reducing agent.

In the reaction $2Na + S ightarrow Na_2S$, sulfur (S) acts as the oxidizing agent. The oxidizing agent is the substance that gains electrons and gets reduced. Here, sulfur changes from an oxidation state of 0 in S to -2 in $Na_2S$, thus gaining electrons and being reduced.

Fluorine (F) is the most electronegative element and it always has an oxidation state of -1 in its compounds. It does not exhibit positive oxidation states in any of its compounds.

Chlorine (Cl), Bromine (Br), and Iodine (I) can have positive oxidation states of +1, +3, and +5 when combined with oxygen. However, they do not have a -1 oxidation state when bonded with oxygen, as oxygen is more electronegative and usually takes the negative oxidation state.

Oxygen typically has a negative oxidation state, but when it combines with Fluorine (F), it can exhibit a positive oxidation state. This is because Fluorine is more electronegative than Oxygen, causing Oxygen to take on a positive oxidation state.

Cesium (Cs) is an alkali metal and always possesses a +1 oxidation state in its compounds. This is because alkali metals lose one electron to achieve a stable noble gas electron configuration.

Oxygen typically exhibits oxidation states of -2, -1, and -1/2 in various compounds. However, it does not possess an oxidation state of +1/2 in any of its compounds.

Carbon can have various oxidation states such as -4, -2, 0, and +4. However, it does not exhibit an oxidation state of +5 in any of its compounds.

Nitrogen can have various oxidation states, but -4 is not one of them. The common oxidation states of nitrogen include -3 (in NH3), -2, -1, 0, +1, +2, +3, +4, and +5 (in HNO3).