|MadSci Network: Chemistry|
Andrew, I hope for your sake you are interested in the intellectual exercise of balancing chemical equations rather than actually playing around with this mixture! Firstly, the word "volatile" in chemistry means something that evaporates easily. It is not a word for reactive or explosive or energy laden. Methanol is volatile, hydrogen peroxide and hydrazine are not particularly volatile (both about the same as water). Secondly, I would remind you that a good chemist always checks out the safety properties of any chemicals s/he is using. Here are some extracts from MSDS sheets: ************ for hydrazine (anhydrous): Stability May be an explosion hazard, particularly if heated. Incompatible with sources of ignition, light, shock, strong oxidizing agents, strong acids, metal oxides, hydrogen peroxide, most common metals, organic materials, porous materials such as wood, paper, asbestos, soil or rust. Toxicology Harmful if inhaled or swallowed. Poison. Probable human carcinogen. Readily absorbed through the skin. May cause severe skin and eye irritation or burns. Long-term exposure may cause CNS, lungs, blood, liver and kidney damage. Typical TLV/TWA 0.1 ppm. Typical STEL 1 ppm. ******** for methanol Stability Stable. May react violently with acids, acid chlorides, acid anhydrides, oxidizing agents, reducing agents and alkali metals. Protect from moisture. Highly flammable. Toxicology Toxic by inhalation, ingestion or skin absorption. May be a reproductive hazard. Ingestion may be fatal. Risk of very serious, irreversible damage if swallowed. Exposure may cause eye, kidney, heart and liver damage. Irritant. Narcotic. UK exposure limits: long-term 200 ppm, short term 250 ppm. ******** for hydrogen peroxide (30% solution) Stability Unstable - readily decomposes to water and oxygen. May develop pressure in the bottle - take care when opening. Forms potentially explosive compounds with ketones, ethers, alcohols, hydrazine, glycerine, aniline, sodium borate, urea, sodium carbonate, triethylamine, sodium fluoride, sodium pyrophosphate and carboxylic acid anhydrides. Materials to avoid include combustibles, strong reducing agents, most common metals, organic materials, metallic salts, alkali, porous materials, especially wood, asbestos, soil, rust, strong oxidizing agents. Toxicology Toxic. Corrosive - can causes serious burns. Eye contact can cause serious injury, possibly blindness. Harmful by inhalation, ingestion and skin contact. Typical OEL 1 ppm. ******** They are three very nasty and dangerous substances! And notice particularly how mixtures of hydrazine and hydrogen peroxide are singled out as unstable and explosive. What that usually means is that you cannot control when such mixtures will go off! So if this mixture is going to be used as a rocket fuel, it would have to be in some complicated liquid fuel design where liquids from different tanks are mixed during flight. They cannot safely be premixed or stored together. If you decide that you want to go ahead with some experimentation after this, then go to your teacher and pass on my recommendation that you need to be banned from the laboratory. ******** Now, to get to your actual question. There are really two quite separate redox reactions going on here. Hydrogen peroxide is the oxidizing agent in both cases. hydrazine and methanol can both act independently or in a concerted fashion as the reducing agents. Reactions like this actually produce quite a mixture of minor products, but the majority and low-energy pathway leads simply to molecular nitrogen, water, and carbon dioxide. So to balance an equation, every H atom has to finish up in H2O, every C atom in CO2, every N atom in N2, and you draw the extra O atoms to make this happen by breaking up hydrogen peroxide into H2O2 --> H2O + [O] thus CH3OH --> CO2 + 2 H2O needs 3 more oxygen atoms, therefore the balanced equation is CH3OH + 3 H2O2 --> CO2 + 5 H2O and N2H4 --> N2 + 2 H2O needs 2 more O atoms, therefore N2H4 + 2 H2O2 --> N2 + 4 H2O
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