Question

Given below are two statements :
Statement I : The higher oxidation states are more stable down the group among transition elements unlike p-block elements.
Statement II : Copper can not liberate hydrogen from weak acids.
In the light of the above statements, choose the correct answer from the options given below

• A. Both Statement I and Statement II are false
• B. Statement I is false but Statement II is true
• C. Both Statement I and Statement II are true
• D. Statement I is true but Statement II is false

Answer 1

The Correct Option is C

To determine the correctness of the given statements, let's analyze each one individually:

1. Statement I: The higher oxidation states are more stable down the group among transition elements unlike p-block elements.
   • In the d-block (transition elements), the trend is generally observed that elements tend to show higher oxidation states as we move down the group. This happens due to the availability of more d orbitals which get increasingly involved in bonding as we move down a group, contributing to higher oxidation states.
   • For example, in Group 6, chromium shows a stable oxidation state of +6 in compounds like CrO₃, while tungsten (W) and molybdenum (Mo), which are below chromium in the periodic table, also exhibit +6 oxidation states in WO₃ and MoO₃, which are quite stable.
   • In contrast, for p-block elements, especially in groups like the nitrogen group, the higher oxidation states become less stable as we go down the group. For example, nitrogen exhibits a stable +5 oxidation state in N₂O₅, while bismuth in the same group predominantly shows the +3 oxidation state with the +5 state being less stable.
   • Hence, Statement I is true.
2. Statement II: Copper cannot liberate hydrogen from weak acids.
   • Copper is less reactive than hydrogen in the electrochemical series. Therefore, it does not easily displace hydrogen ions from acidic solutions, including weak acids, to liberate hydrogen gas.
   • This property is seen because copper will not react with the hydrogen ions without a higher impetus, which weak acids do not provide. Stronger acids like hydrochloric acid can oxidize copper in the presence of oxygen or another oxidizing agent rather than just displacing hydrogen.
   • Thus, Statement II is also true.

By reviewing both statements, it is clear that both Statement I and Statement II are true. Therefore, the correct answer is: Both Statement I and Statement II are true.

Answer 2

- Statement I: Transition metals tend to have more stable higher oxidation states as we move down the group due to the increasing availability of d-orbitals. This is in contrast to p-block elements, where higher oxidation states become less stable down the group.
- Statement II: Copper can indeed liberate hydrogen from weak acids such as hydrochloric acid, which is true for copper in the form of copper(I) chloride.
Thus, both statements are true, and the correct answer is (3).