Question

Solutions containing nickel(II) ion are usually bright green in color. When potassium hydroxide is added to such a nickel(II) solution, a pale-green fluffy solid forms and settles out of the solution. The fact that a solution of nickel(II) ion is bright green is an example of a property.

Short answer

The bright green color of the nickel(II) ion solution is an example of a chemical property. When potassium hydroxide (KOH) is added to the solution, it reacts with the nickel(II) ions to form a pale-green fluffy solid called nickel(II) hydroxide (Ni(OH)_2), as shown in the balanced chemical equation: \( Ni^{2+} + 2 KOH \rightarrow Ni(OH)_2 + 2 K^+ \). This solid settles out of the solution due to its low solubility in water, and its formation indicates a chemical change has taken place.

Step-by-step solution

Recognize the nickel(II) ion property

In the given exercise, the bright green color of the nickel(II) ion solution is an example of a chemical property. This color indicates the presence of nickel(II) ions (Ni^2+) in the solution.

Identify the reaction with potassium hydroxide

When potassium hydroxide (KOH) is added to the nickel(II) ion solution, a chemical reaction occurs. Potassium hydroxide is a strong base, which reacts with the nickel(II) ions to form a pale-green fluffy solid.

Write the chemical equation for the reaction

To understand the reaction better, we will write the balanced chemical equation for the reaction between nickel(II) ions and potassium hydroxide. The equation is as follows: \( Ni^{2+} + 2 KOH \rightarrow Ni(OH)_2 + 2 K^+ \) In this equation, the nickel(II) ion (Ni^2+) reacts with potassium hydroxide (KOH) to form nickel(II) hydroxide (Ni(OH)_2), a pale-green fluffy solid, and potassium ions (K^+).

Explain the formation of the pale-green fluffy solid

The pale-green fluffy solid formed in the reaction is nickel(II) hydroxide (Ni(OH)_2). It forms as a result of the reaction between the nickel(II) ion and potassium hydroxide. The solid settles out of the solution due to its low solubility in water.

Understand the significance of the chemical property

The bright green color of the nickel(II) ion solution is an example of a chemical property that can help in the identification of the presence of nickel(II) ions. When a chemical reaction occurs, the formation of a new substance with different properties, such as the pale-green fluffy nickel(II) hydroxide, indicates that a change has taken place.

Key concepts

Chemical Properties

Chemical properties are characteristics of a substance that are observed during a reaction when the substance's chemical composition is changed. These properties can include

• color changes,
• reactivity with other chemicals,
• flammability, and
• the ability to oxidize.

For instance, in the context of nickel(II) ions, the bright green color of the nickel(II) ion solution is a distinctive chemical property. It indicates the presence of nickel(II) ions (\( Ni^{2+} \) in water). This colorful trait helps in quickly identifying nickel(II) ions amidst other chemical reactions or tests.
This property is utilized in various analytical techniques where visual cues are critical. Such a property is important not only for identification but also for understanding the behavior of substances in various chemical reactions.

Nickel(II) Ions

Nickel(II) ions, denoted as \( Ni^{2+} \), play a significant role in many chemical reactions due to their unique characteristics. These ions are formed when a nickel atom loses two electrons, resulting in a 2+ charge.
Nickel(II) ions are typically found in aqueous solutions as part of various compounds and exhibit a bright green coloration, which is their signature feature. The presence of nickel(II) ions is not only visually noticeable but also detectable through various analytical methods.

• They often participate in formation of bright colored complexes and compounds.
• Their behavior in solutions includes a tendency to form insoluble precipitates when reacted with certain compounds.
• They are used in electroplating and battery production industries.

Understanding nickel(II) ions is crucial for predicting their interactions in chemical solutions and environments.

Precipitation Reaction

Precipitation reactions are chemical reactions where an insoluble solid forms and separates from a solution. In terms of the exercise, when potassium hydroxide (KOH) is added to a nickel(II) ion solution, a precipitation reaction occurs. The reaction involves nickel(II) ions reacting with hydroxide ions to produce an insoluble solid called nickel(II) hydroxide (\( Ni(OH)_2 \)).
The balanced chemical equation for this precipitation reaction is:\[Ni^{2+} + 2 KOH \rightarrow Ni(OH)_2 + 2 K^{+}\]
In this equation:

• \( Ni^{2+} \) represents nickel(II) ions.
• \( KOH \) symbolizes potassium hydroxide, a strong base.
• \( Ni(OH)_2 \) is nickel(II) hydroxide, the pale-green solid precipitate.
• \( K^{+} \) are the resulting potassium ions in the solution.

The formation of this solid, often a fluffy precipitate, is due to its low solubility in water. Precipitation reactions are important for removing ions from solutions and understanding the solid formation during chemical reactions.