Question

The mixture of which of the following can produce blue colouration? (a) Iron (III) chloride and \(\mathrm{K}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]\) (aq) (b) \(\mathrm{NH}_{4} \mathrm{OH}\) (aq) and \(\mathrm{CuSO}_{4}\) (aq) (c) Adding anhydrous \(\mathrm{CuSO}_{4}\) to water (d) \(\mathrm{ZnCl}_{2}\) (aq) and \(\mathrm{K}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right](\mathrm{aq})\)

Short answer

Options (a), (b), and (c) produce blue coloration.

Step-by-step solution

Understand the Question

Determine which mixture results in a blue coloration. This is a problem about chemical reactions that produce a specific visual result.

Analyze Option (a)

For option (a), Iron (III) chloride when mixed with potassium ferricyanide \([K_4[Fe(CN)_6]\) results in a Prussian blue color, which is a dark blue pigment.

Analyze Option (b)

Ammonium hydroxide \((NH_4OH)\) and copper sulfate \((CuSO_4)\) will react to form a light blue complex of copper hydroxide \((Cu(OH)_2)\) precipitate.

Analyze Option (c)

Anhydrous copper sulfate is white, but when water is added, it forms hydrated copper sulfate, which is blue, though this is not due to a chemical reaction but a hydration process.

Analyze Option (d)

Zinc chloride \((ZnCl_2)\) and potassium ferricyanide \([K[Fe(CN)_6]]\) do not produce a blue color when mixed.

Identify the Correct Option

Based on the analysis, options (a), (b), and (c) can all result in a blue or blue-related color due to the reactions or processes described above.

Key concepts

Prussian Blue Formation

Prussian Blue is a fascinating dark blue pigment that has a rich history both in art and in science. This compound forms when iron (III) chloride (
) reacts with potassium ferricyanide. The reaction results in a beautiful blue complex, primarily composed of iron and cyanide ions arranged in a unique coordination network.

• The chemical reaction involved is: detouring from iron(III) chloride the process.
• This particular reaction forms a coordination compound known as Prussian Blue.
• The blue color arises from the movement of electrons between different states or orbitals within the compound.

Historically, Prussian Blue was used as a pigment for paintings and is revered for its rich and vibrant color. However, its role isn't just confined to art. In chemistry, it serves as a model study for examining physical and chemical properties of coordination compounds.

Coordination Compounds

Coordination compounds like Prussian Blue consist of a central metal atom or ion surrounded by molecules or anions, known as ligands. These compounds exhibit unique properties due to the specific arrangement of the metal and ligands.

• The formation of these compounds is governed by Lewis acid-base principles.
• In Prussian Blue, potassium ferricyanide works as a complex-forming agent that coordinates with iron ions to create a stable structure.
• The resulting compound is a type of coordination polymer with interesting properties, including the striking blue color.

Coordination compounds are essential in various applications ranging from catalysis to pharmaceutical uses. Their unique bonding and the resulting color changes have broad implications in both industry and research, helping scientists better understand chemical behaviors and develop new technologies.

Color Change in Chemistry

Color changes in chemistry are not just visually appealing but also signify underlying chemical phenomena. These changes often occur due to electronic transitions, complex formation, or the presence of specific ions.

• When iron (III) chloride reacts with potassium ferricyanide, a vivid blue color is produced, signaling the formation of Prussian Blue.
• In another example, although less about a chemical reaction, adding water to anhydrous copper sulfate changes its appearance from white to blue due to hydration.
• These colors are used as indicators in various chemical processes and can help identify substances or predict their behavior in solutions.

Understanding these changes can be vital in chemistry, where visual cues are used for qualitative analysis and monitoring reactions. Such color transformations not only enhance the understanding of compounds but also add to the depth and richness of chemical education.