Which of the following is most basic?

Question

Statement-I : Consider the following pairs of ions $(\text{Sc}^{3+}, \text{Ti}^{3+}), (\text{Ti}^{4+}, \text{Ni}^{2+}), (\text{Cu}^{2+}, \text{Zn}^{2+})$ and $(\text{Cr}^{3+}, \text{Mn}^{3+})$. Out of these pairs three pairs consist of ions that are both coloured :
Statement-II : Among the lanthanide ions $\text{Eu}^{2+}$, $\text{Gd}^{3+}$, $\text{Ce}^{4+}$ and $\text{Tb}^{4+}$, the ion $\text{Tb}^{4+}$ is the strongest reducing agent.
Choose the correct option.

Answer 1

Step 1: Conceptual Understanding:
The basicity of metal oxides depends on the oxidation state of the metal in the oxide. As a general rule, there is an inverse relationship between the basicity of the oxide and the oxidation state of the metal. This means that metals in lower oxidation states tend to form oxides that are more basic, while metals in higher oxidation states generally form oxides that are more acidic. The reason for this lies in the nature of the metal-oxygen bond.
When the metal is in a lower oxidation state, the metal-oxygen bond is typically ionic in character, which makes the oxide basic. On the other hand, when the oxidation state of the metal is higher, the metal-oxygen bond becomes more covalent, which leads to acidic or amphoteric oxides.
Step 2: Detailed Explanation:
Let's break this down further with specific examples. In the case of transition metals, such as manganese (Mn), the oxidation state plays a crucial role in determining the oxide's properties. When the oxidation state of manganese is $ +2 $, as in the oxide $ MnO $, the metal-oxygen bond is ionic, and the oxide exhibits basic properties. This is because the $ Mn^{2+} $ ion can easily donate electron pairs to water molecules, making the oxide capable of acting as a base.
As the oxidation state of manganese increases to $ +7 $, as seen in $ Mn_2O_7 $, the situation changes. The metal-oxygen bond becomes increasingly covalent due to the higher oxidation state, and this oxide shows acidic behavior. $ Mn_2O_7 $ is highly acidic because the $ Mn^{7+} $ ion has a strong tendency to attract electrons, making the oxide capable of reacting with water to form an acidic solution.
Thus, we can see that the basicity or acidity of the metal oxide is closely related to the oxidation state of the metal, with lower oxidation states being more basic and higher oxidation states being more acidic or amphoteric.
Step 3: Final Answer:
Among the given examples, the most basic oxide is $ MnO $, which corresponds to manganese in its lowest oxidation state of $ +2 $. In this state, the oxide is ionic and shows basic properties. As the oxidation state increases to $ +7 $ in $ Mn_2O_7 $, the oxide becomes more acidic, thus demonstrating the inverse relationship between oxidation state and basicity. Therefore, $ MnO $ is the most basic oxide in this case.

Which of the following is most basic?

Show Hint

The Correct Option is C

Solution and Explanation

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