Question

Hydrazine is somewhat toxic. Use the half-reactions shown below to explain why household bleach (a highly alkaline solution of sodium hypochlorite) should not be mixed with household ammonia or glass cleansers that contain ammonia. \(\mathrm{ClO}^{-}+\mathrm{H}_{2} \mathrm{O}+2 \mathrm{e}^{-} \longrightarrow 2 \mathrm{OH}^{-}+\mathrm{Cl}^{-} \quad \mathscr{E}^{\circ}=0.90 \mathrm{~V}\) \(\mathrm{N}_{2} \mathrm{H}_{4}+2 \mathrm{H}_{2} \mathrm{O}+2 \mathrm{e}^{-} \longrightarrow 2 \mathrm{NH}_{3}+2 \mathrm{OH}^{-} \quad \mathscr{E}^{\circ}=-0.10 \mathrm{~V}\)

Short answer

In short, mixing household bleach containing sodium hypochlorite (ClO⁻) with ammonia (NH₃) results in a spontaneous redox reaction with a positive potential of 1.00 V, forming the highly toxic and volatile compound nitrogen trichloride (NCl₃). Thus, they should not be mixed due to the potential hazards to human health posed by the toxic product.

Step-by-step solution

Identify the Redox Reaction

To determine the reaction that occurs when household bleach and ammonia are mixed, we must first combine the given half-reactions: 1. \(\mathrm{ClO}^{-}+\mathrm{H}_{2}\mathrm{O}+2e^{-}\rightarrow 2\mathrm{OH}^{-}+\mathrm{Cl}^{-} \quad \mathscr{E}^{\circ}=0.90 V \) 2. \(\mathrm{N}_{2}\mathrm{H}_{4}+2\mathrm{H}_{2}\mathrm{O}+2e^{-}\rightarrow 2\mathrm{NH}_{3}+2\mathrm{OH}^{-} \quad \mathscr{E}^{\circ}=-0.10 V \)

Balance the Electrons

To combine the two half-reactions, we need an equal number of electrons on both reactions. The first reaction has 2 electrons, and the second reaction also has 2 electrons. Therefore, the half-reactions are already balanced.

Add the Half-Reactions

Next, we will add the two half-reactions together: \(\mathrm{ClO}^{-}+\mathrm{H}_{2}\mathrm{O}+2e^{-}\rightarrow 2\mathrm{OH}^{-}+\mathrm{Cl}^{-}\) \(\mathrm{N}_{2}\mathrm{H}_{4}+2\mathrm{H}_{2}\mathrm{O}+2e^{-}\rightarrow 2\mathrm{NH}_{3}+2\mathrm{OH}^{-}\) Add the equations to get the full redox reaction: \(\mathrm{ClO}^{-}+\mathrm{N}_{2}\mathrm{H}_{4}+3\mathrm{H}_{2}\mathrm{O}\rightarrow 2\mathrm{NH}_{3}+4\mathrm{OH}^{-}+\mathrm{Cl}^{-}\)

Determine the Reaction's Potential

Since we have the standard potentials \(\mathscr{E}^{\circ}\) for each half-reaction, we can calculate the overall reaction potential: \(\Delta \mathscr{E}^{\circ} = \mathscr{E}^{\circ}_{cathode} - \mathscr{E}^{\circ}_{anode} = 0.90 V - (-0.10 V) = 1.00 V\) Since the overall reaction potential is positive, the reaction is spontaneous, and the toxic product will be formed when bleach and ammonia are mixed.

Identify the Toxic Product

From the balanced redox equation, we can identify the toxic product formed as a result of the reaction. When bleach containing sodium hypochlorite (ClO⁻) and ammonia (NH₃) are mixed, nitrogen trichloride (NCl₃) is produced. Nitrogen trichloride is a highly toxic and volatile compound which poses hazards to human health. In conclusion, household bleach containing sodium hypochlorite should not be mixed with ammonia or glass cleansers containing ammonia due to the formation of toxic nitrogen trichloride in the resulting redox reaction.

Key concepts

Household Chemicals

Household chemicals are a common part of our daily lives. They include a wide range of products from cleaning agents, like bleach and ammonia, to personal care items and garden supplies. These chemicals are used for their powerful cleaning properties and disinfectant capabilities. For example, bleach, particularly sodium hypochlorite, is excellent for sanitizing surfaces and killing bacteria. Ammonia is often found in glass cleaners, valued for its ability to remove grime and streaks from windows. Despite their usefulness, it is essential to understand how they can react with each other. Mixing certain household chemicals can sometimes lead to unexpected or dangerous reactions. This is why it's crucial to read labels and understand the properties of each chemical you are using.

Toxic Compounds

Toxic compounds can be formed when certain household chemicals are mixed. A significant danger arises when bleach and ammonia, common household cleaning agents, are combined. This combination leads to the production of toxic compounds, such as chloramines and nitrogen trichloride. Nitrogen trichloride ( Cl_3 ) is especially hazardous. It is a volatile and explosive chemical that can cause harm to human health. Exposure to toxic compounds like nitrogen trichloride can lead to symptoms such as coughing, irritation of the eyes and respiratory system, and potentially more severe health risks. For these reasons, it is important to be aware of the potential toxic products that can form from mixing everyday chemicals.

Chemical Safety

Chemical safety is a critical aspect of using household chemicals effectively and responsibly. To ensure safe use, it is vital to follow a few guidelines:

• Always read and follow the label instructions on chemical products.
• Understand the risks of mixing common cleaning agents.
• Store chemicals safely, out of reach of children and pets.
• Use protective gear, like gloves and masks, when handling potent chemicals.
• Ensure proper ventilation when using chemicals indoors.

By adhering to these safety tips, you can prevent hazardous situations and ensure a safe home environment. Awareness and education on the safe use of chemicals can significantly reduce the risk of accidents.

Reaction Mechanism

The reaction mechanism involving household bleach and ammonia is a type of redox reaction, which involves the transfer of electrons between two substances. When bleach (sodium hypochlorite) and ammonia come into contact, their individual chemical properties lead to a transfer of electrons, creating new compounds. Specifically, the hypochlorite ion ( ClO^- ) from bleach acts as an oxidizing agent, while ammonia could act as a reductant. This results in the spontaneous formation of products like nitrogen trichloride under certain conditions. Understanding the reaction mechanism helps in predicting the products of chemical reactions, which is essential for preventing the formation of hazardous compounds during everyday cleaning. The positive overall reaction potential of the bleach and ammonia mixture indicates the spontaneity and likelihood of this reaction occurring, emphasizing why these chemicals should not be combined.