MadSci Network: Chemistry

Re: Balancing hydrazine, methyl alcohol, and hydrogen peroxide

Date: Wed Nov 7 23:59:17 2001
Posted By: John Christie, Faculty, School of Chemistry, La Trobe University, Bundoora, Victoria, Australia
Area of science: Chemistry
ID: 1004494096.Ch

Andrew, I hope for your sake you are interested in the intellectual exercise of 
balancing chemical equations rather than actually playing around with this 

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 

for hydrazine (anhydrous):

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. 

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

Stable. May react violently with acids, acid chlorides, acid anhydrides, 
oxidizing agents, reducing agents and alkali metals. Protect from moisture. 
Highly flammable. 

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)

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. 

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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