[CU(H_2O)_4]^{2+} + H_2O \rightleftharpoons Write the equation for the following acting as an acid.
Answer (2)
The complex ion [ C u ( H 2 O ) 4 ] 2 + acts as an acid by donating a proton to water.
This forms a hydronium ion ( H 3 O + ) and a complex ion with a hydroxide ligand.
The chemical equation is: [ C u ( H 2 O ) 4 ] 2 + ( a q ) + H 2 O ( l ) ⇌ [ C u ( H 2 O ) 3 ( O H ) ] + ( a q ) + H 3 O + ( a q ) .
The overall charge of the complex ion decreases by one unit.
[ C u ( H 2 O ) 4 ] 2 + ( a q ) + H 2 O ( l ) ⇌ [ C u ( H 2 O ) 3 ( O H ) ] + ( a q ) + H 3 O + ( a q )
Explanation
Understanding the Problem We are given the complex ion [ C U ( H 2 O ) 4 ] 2 + and asked to write the equation for its reaction as an acid in water.
The Acidic Behavior When acting as an acid, the complex ion will donate a proton ( H + ) from one of its coordinated water ligands to a water molecule in the solution. This will result in the formation of a hydronium ion ( H 3 O + ) and a complex ion with one less water ligand and one hydroxide ligand ( O H − ).
Writing the Chemical Equation The chemical equation for the deprotonation of the complex ion is:
[ C u ( H 2 O ) 4 ] 2 + ( a q ) + H 2 O ( l ) ⇌ [ C u ( H 2 O ) 3 ( O H ) ] + ( a q ) + H 3 O + ( a q )
In this equation, one of the coordinated water molecules loses a proton, forming a hydroxide ligand ( O H − ). The overall charge of the complex ion decreases by one unit from +2 to +1.
Examples
Understanding how metal ions behave as acids is crucial in many chemical and biological processes. For example, in environmental chemistry, the acidity of metal ions in water can affect the solubility and toxicity of pollutants. In biochemistry, metal ions play a key role in enzyme catalysis, where their ability to donate or accept protons can influence reaction rates and mechanisms. This concept is also important in industrial applications, such as water treatment and the synthesis of metal-containing compounds.
The complex ion [ C u ( H 2 O ) 4 ] 2 + acts as an acid by donating a proton to water, resulting in the formation of a hydronium ion and a hydroxo complex. The balanced equation for this reaction is [ C u ( H 2 O ) 4 ] 2 + ( a q ) + H 2 O ( l ) ⇌ [ C u ( H 2 O ) 3 ( O H ) ] + ( a q ) + H 3 O + ( a q ) . This illustrates the ion's role in acid-base chemistry.
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