Question

Hydrazine is somewhat toxic. Use the following half-reactions to explain why household bleach (highly alkaline solutions 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

When household bleach (sodium hypochlorite) is mixed with ammonia or cleansers containing ammonia (in the form of hydrazine), the reaction produces ammonia (\(\mathrm{NH}_3\)) and hydroxide ions (\(\mathrm{OH}^-\)). However, the presence of hydroxide ions may lead to the formation of toxic chloramine gas (\(\mathrm{NH}_2\mathrm{Cl}\)) and nitrogen trichloride (\(\mathrm{NCl}_3\)) as side reactions, which can cause respiratory irritation. Therefore, it is not recommended to mix household bleach with ammonia or glass cleansers containing ammonia due to the possible formation of toxic chemical species.

Step-by-step solution

Balance the given half-reactions

We are given two half-reactions: \( \mathrm{ClO}^{-}+\mathrm{H}_{2} \mathrm{O}+2 \mathrm{e}^{-} \longrightarrow 2 \mathrm{OH}^{-}+\mathrm{Cl}^{-} \quad \mathscr{E}^{\circ}=0.90 \mathrm{V} \) \( \mathrm{N}_{2} \mathrm{H}_{4}+2 \mathrm{H}_{2} \mathrm{O}+2 \mathrm{e}^{-} \longrightarrow 2 \mathrm{NH}_{3}+2 \mathrm{OH}^{-} \quad \mathscr{E}^{\circ}=-0.10 \mathrm{V} \) Note that both half-reactions are already balanced in terms of mass and charge.

Combine the half-reactions to obtain the full redox reaction

Since the number of electrons transferred in both half-reactions is equal (2 electrons), we can add the two half-reactions directly: \[ \begin{aligned} \mathrm{ClO}^{-}+\mathrm{H}_{2} \mathrm{O}+2 \mathrm{e}^{-} & \longrightarrow 2 \mathrm{OH}^{-}+\mathrm{Cl}^{-} \\ \mathrm{N}_{2} \mathrm{H}_{4}+2 \mathrm{H}_{2} \mathrm{O}+2 \mathrm{e}^{-} & \longrightarrow 2 \mathrm{NH}_{3}+2 \mathrm{OH}^{-} \end{aligned} \] Adding the half-reactions, the final redox reaction is: \[ \mathrm{ClO}^{-}+\mathrm{N}_{2} \mathrm{H}_{4}+3 \mathrm{H}_{2} \mathrm{O} \longrightarrow 2 \mathrm{NH}_{3}+2 \mathrm{OH}^{-}+\mathrm{Cl}^{-} \]

Analyze the chemical species formed in the reaction

In the reaction obtained in Step 2, when household bleach (sodium hypochlorite) is mixed with ammonia or cleansers containing ammonia (in the form of hydrazine), the product formed is ammonia (\(\mathrm{NH}_3\)) and hydroxide ions (\(\mathrm{OH}^-\)). However, the presence of hydroxide ions in the reaction mixture may lead to the formation of toxic chloramine gas (\(\mathrm{NH}_2\mathrm{Cl}\)) and nitrogen trichloride (\(\mathrm{NCl}_3\)) as side reactions. These compounds are toxic and can cause respiratory irritation. Therefore, based on the full redox reaction and the possible side products formed, it is not recommended to mix household bleach with ammonia or glass cleansers containing ammonia due to the possible formation of toxic chemical species.

Key concepts

Household Chemicals Safety

Mixing common household chemicals can sometimes be dangerous. Knowing which products not to mix is crucial for safety. Many household cleaning products contain chemicals that react with each other to produce harmful byproducts. For example, mixing bleach with ammonia can lead to the formation of toxic gases like chloramine. Household bleach is a solution of sodium hypochlorite, which is an oxidizing agent. When it encounters ammonia, present in many glass cleaners and other household products, a reaction can lead to the evolution of irritating and potentially dangerous gases.

It's important to always read and follow label instructions on cleaning products. Never mix cleaning solutions unless the label specifically says it's safe. Also, ensure that the room is well ventilated when using products that contain bleach or ammonia. Keeping these safety measures in mind can help prevent accidental exposure to hazardous conditions.

Chemical Reactions in Everyday Products

Chemical reactions are all around us, even in the products we use daily. Each cleaning agent is designed with specific chemical properties to tackle different types of dirt and germs. Bleach, a strong disinfectant, and ammonia, an effective cleaning agent, both work through chemical reactions.

Bleach works by oxidizing substances it comes into contact with, thus killing bacteria and breaking down stains. Ammonia dissolves grime and grease, making it valuable for cleaning glass and surfaces without streaks. Despite their effectiveness separately, the chemical interaction between bleach and ammonia can lead to a harmful reaction, producing chloramine gases. It's these kinds of reactions that highlight the importance of understanding the chemical nature of everyday products.

Toxic Byproducts of Chemical Reactions

Many chemical reactions can produce byproducts that are toxic to humans and pets. When bleach is mixed with ammonia, one of the notable byproducts is chloramine gas. Chloramine is a group of chemical compounds that have harmful effects on the respiratory system. The exposure to these gases can cause symptoms like coughing, shortness of breath, and irritation of the eyes, nose, and throat.

Nitrogen trichloride, another potential byproduct of the reaction between bleach and ammonia, is also hazardous. It's crucial to be aware of these byproducts, as they underscore the dangers of careless chemical mixing. Knowing the chemistry behind these reactions helps prevent accidents and ensures safe usage of household cleaners. Remember, when in doubt, keep cleaning agents separate and always ventilate the area thoroughly.