The complete reaction of 2.60 g of chromium metal with 50.00 mL of 1.200 M H2SO4 in the absence of air gave a blue solution and a colorless gas that was collected at 25°C and a pressure of 735 mm Hg. (e) When an excess of KCN is added to the solution, the color changes, and the paramagnetism of the solution
decreases. Explain.

검증된 단계별 안내

Identify the initial reaction: Chromium (Cr) reacts with sulfuric acid (H2SO4) to produce chromium sulfate (Cr2(SO4)3) and hydrogen gas (H2).

Recognize that the blue solution is likely due to the formation of a chromium(III) complex, such as [Cr(H2O)6]^{3+}.

Understand that the addition of an excess of KCN leads to the formation of a new complex, [Cr(CN)6]^{3-}, which is less paramagnetic.

Explain that the decrease in paramagnetism is due to the fact that the cyanide complex has a lower number of unpaired electrons compared to the initial chromium complex.

Conclude that the color change and decrease in paramagnetism are due to the formation of a different chromium complex with cyanide ligands, which alters the electronic structure and properties of the solution.

비슷한 문제에 대한 검증된 영상 답변:

이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Redox Reactions

Redox reactions involve the transfer of electrons between substances, leading to changes in oxidation states. In the given reaction, chromium metal is oxidized while sulfuric acid is reduced, resulting in the formation of a blue solution and a colorless gas, likely hydrogen. Understanding the electron transfer is crucial for analyzing the chemical changes occurring in the reaction.

Paramagnetism

Paramagnetism is a form of magnetism that occurs in materials with unpaired electrons, which can be attracted by an external magnetic field. The presence of unpaired electrons in transition metal complexes, such as those formed with chromium, contributes to the solution's paramagnetic properties. The addition of KCN alters the electronic structure of the chromium complex, reducing the number of unpaired electrons and thus decreasing paramagnetism.

Complex Ion Formation

Complex ions are formed when metal ions coordinate with ligands, which are molecules or ions that can donate electron pairs. In this case, KCN acts as a ligand that binds to chromium ions in the solution, leading to the formation of a new complex. This interaction not only changes the color of the solution but also affects its magnetic properties, illustrating the significance of ligand interactions in coordination chemistry.