Question

The hair dyes available in the market generally contain two bottles, one containing the dye and the other hydrogen peroxide. Before applying the dye, the two solutions are mixed. The hydrogen peroxide (1) is added to dilute the solution of the dye (2) oxidises the dye to give the desired colour (3) reduces the dye to give the desired colour (4) acidifies the solution of the dye

Short answer

Option (2) oxidises the dye to give the desired colour.

Step-by-step solution

Analyzing the Function of Hydrogen Peroxide

Hydrogen peroxide is a common oxidizing agent. The role of an oxidizing agent is to cause another substance to lose electrons. In the context of hair dye, this means potentially facilitating a color change by oxidizing the dye.

Eliminating Options with Incorrect Mechanisms

Options (1) and (4) suggest hydrogen peroxide dilutes or acidifies the dye solution, which are not the primary chemical roles of hydrogen peroxide. Therefore, these can be ruled out.

Choosing Between Oxidation and Reduction

The remaining options (2) and (3) involve oxidation and reduction processes. Hydrogen peroxide is widely known for its oxidative properties rather than reductive.

Identifying the Correct Role

Since hydrogen peroxide oxidizes other substances, the suitable function in hair dye is option (2) which is 'oxidises the dye to give the desired colour'.

Key concepts

Hydrogen Peroxide

Hydrogen peroxide (H₂O₂) is a versatile chemical with a wide array of applications, ranging from disinfecting wounds to bleaching hair. Its chemical structure is made up of two hydrogen atoms and two oxygen atoms. Due to the presence of an oxygen-oxygen single bond, it is an excellent oxidizing agent. This property allows it to donate oxygen to other substances, causing them to lose electrons.

In the context of hair dye, hydrogen peroxide plays a critical role. When you mix the dye with hydrogen peroxide, it facilitates the oxidation process necessary to alter the color of your hair. It essentially helps to open up the hair cuticle, enabling the dye to penetrate deeply and offer long-lasting color transformation.

This oxidizing ability means it is predominantly used to ensure the hair dye develops the desired hue on your hair, making it an essential component in hair dye kits.

Here’s a brief overview of hydrogen peroxide’s characteristics:

• Formula: H₂O₂
• Properties: Colorless and slightly more viscous than water
• Uses: Disinfectant, bleaching agent, and an oxidizing agent

Chemical Reactions

Chemical reactions are processes where reactants are transformed into products. These reactions are fundamental to all chemical processes, including those involving hydrogen peroxide in hair dyeing.

When you mix the dye with hydrogen peroxide, several chemical reactions occur, primarily oxidative reactions. In these reactions, hydrogen peroxide donates oxygen atoms, which helps in breaking down the natural color pigments in your hair and facilitates the bonding of the new dye pigments to your hair.

Without these chemical reactions, the hair dye wouldn’t be able to penetrate your hair shaft properly and deposit the color effectively.

Key aspects of chemical reactions include:

• Reactants: Substances that undergo change (e.g., hydrogen peroxide and the hair dye)
• Products: New substances produced from the reaction (e.g., the altered hair color)
• Oxidation: A specific type of reaction where a substance loses electrons

Oxidation Process

The oxidation process is crucial in many chemical reactions, including those involving hydrogen peroxide. Oxidation refers to the loss of electrons by a molecule, atom, or ion. This process is often paired with another process called reduction, where another substance gains the electrons.

In the context of hair dyeing, the oxidation process facilitated by hydrogen peroxide leads to the desired color change in the dye. When hydrogen peroxide oxidizes the dye, it helps to break down the natural color molecules in your hair and enables the new color molecules to bond more effectively.

Some key points about the oxidation process are:

• Involves the loss of electrons from a substance
• Often involves the addition of oxygen or removal of hydrogen
• Crucial for effective hair dyeing, making the dye molecules more reactive and able to bond with hair

The efficiency of the oxidation process is why hydrogen peroxide is such a critical component in hair dye solutions, ensuring a long-lasting and vibrant color in your hair.