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Questions tagged [combustion]

For questions about the combustion of an organic molecule or inorganic substance. Do not use this tag if your question is about the [stoichiometry] of a combustion reaction, or for the calculations of [thermodynamics] functions (like enthalpy change).

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Fire Prevention [closed]

You are presented with two identical containers of 5 litre capacity and each half full. The cans contain gasoline flashpoint −43 °C, methyl alcohol flashpoint 11 °C. What would happen if you dropped a ...
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Why does Magnesium burn hotter than other Group II metals?

It seems apparent, when one performs the standard "flame tests" in a lab, for the Group II elements that Magnesium burns by far the hottest and brightest. Why is this true? I wouldn't expect this at ...
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Percent hydrogen and carbon [closed]

A 1 g sample of an organic compound was burned in a combustion analyzer and yielded 1.42 g carbon dioxide and 0.872 g of water. Calculate the percent carbon and hydrogen in the sample. From the ...
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Dioxin synthesis in a rocket stove riser?

I'm building a rocket stove for cooking with a wok at the top of the riser. At the top of the riser I'm seeing temperatures of 500-700 deg C, and I believe at the bottom it's likely under 1000 deg C (...
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Determining chemical formula of the hydrocarbon via combustion analysis [duplicate]

A container of volume $15\ \mathrm{L}$ contains a hydrocarbon at $27\ ^\circ\mathrm{C}$ and $2\ \mathrm{atm}$ pressure. For the analysis, we take $10\ \mathrm{g}$ of hydrocarbon and the pressure ...
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33 views

What would happen if you burned paper with a laser, in a vacuum?

If you hit a piece of paper with a powerful laser inside a vacuum, what would happen? It sounds like it should not "burn" and have a flame spread over the paper, as there is, of course, no oxygen. ...
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59 views

Flow rate of the fuel consisting of ethanol and water burning in air of a given flow rate

I hope that someone could give me some hints or tips on how to approach this question, even though these types of questions are usually closed off as homework. A burner is run by a fuel mixture of $...
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Is it possible to convert a combustion reaction directly into an electrochemical one?

I'm fairly inexperienced in chemistry so forgive me if this question is silly but, why is it not possible to convert a combustion reaction to an electrochemical one directly and harvest the electrical ...
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Atomic carbon in rocket exhaust

Inspired by this article, I've been looking at using metallic hydrogen as a rocket fuel using CEARUN. I'm looking at diluting the atomic hydrogen with liquid methane to reduce the chamber temperature ...
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1answer
45 views

Decomposition vs Combustion reaction

I'm balancing chemical equations, and I came across the following: $$\ce{O2 + C4H9NH2 -> CO2 + H2O + N2}\tag{unbalanced}$$ My initial reaction was that it is a combustion reaction. According to ...
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Carbon monoxide from activated charcoal filters

We use activated charcoal in air filters of the ventilation system to remove pollutant vapours from the exhaust air. Before the filters, the air is heated a bit to avoid condensation of water. ...
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What governs the amount of smoke produced by an extinguished match?

First Chemistry question, so apologies if this isn't quite in the spirit of this SE. I have noticed that when extinguishing a lit match by blowing it out, the amount of smoke produced can vary widely....
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Rate equation of a radical

Consider the following elementary reaction mechanism where both the forward and reverse reaction mechanism are important $$\ce{CO + O2<->[1] CO2 + O}$$ $$\ce{O + H2O<->[2] OH + OH}$$ ...
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1answer
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What is the molar enthalpy? [closed]

In a practice test there's the question, 'Given that the combustion of.305g of glucose causes a raise of temperature of 6.30C of a caloromiter with total heat capacity C=755J/C and the molecular ...
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Why does wood burn but not sugar?

Fundamentally, they're both carbohydrates, although the cellulose in wood is essentially polymerized glucose, which combined with its isomer fructose forms sucrose. So why does wood readily burn ...
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1answer
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How could I produce/rig this flame-colour lottery?

Not sure if this is the wrong SE for this, happy to move it if not... In the Netflix TV series Sabrina, there is a scene where people take part in an appropriately-gothic-and-ominous lottery, which ...
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3answers
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Combustion analysis methodology question

I am questioning the answer key of an exam question my chemistry professor has given, because I think there is a flaw in the methodology of the exam answer. I have worked out my solution using my ...
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1answer
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Are there gases that spontaneously combust when mixed with oxygen? [closed]

Is there a known gas that would combust by there mere action of mixing with oxygen? So, we could put this hypothetical gas in a balloon, and if the balloon popped, it would combust and explode.
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1answer
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Is flour or baking soda really suitable for extinguishing grease fires?

I think most have heard the advise that you should put flour (or baking soda) on a grease fire to absorb the oil before. While this is certainly better than using water, I'm skeptical. For starters ...
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1answer
64 views

Calorific value of a gas in combustion

The Wikipedia article on heat of combustion says: The calorific value [...] may be expressed with the quantities: energy/mole of fuel energy/mass of fuel energy/volume of the fuel ...
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1answer
70 views

How is the light from a fire emitted?

When you see a fire burning, you have wood (fuel) interacting with oxygen which (through a chemical reaction) gives off heat - and light. But the light appears to emit at some point well-away from ...
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1answer
290 views

What is the mechanism of alkane combustion?

I understand that combustion of hydrocarbons (such as alkanes) produces energy by breaking bonds: $$\ce{C_nH_{2n} + $\frac{3n}{2}$ O2 -> nCO2 + n H2O}$$ And I can find dozens of explanations of ...
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Is sodium “also known to turn purple and combust (like lithium),” when exposed to water?

I understand that indicator solutions can change color depending on pH, but the following statements in the Phys.org article Super cheap earth element to advance new battery tech to the industry has ...
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373 views

Do all flames require the same minimum concentration of oxygen to sustain themsleves?

Assume you have burned some substance A in an airtight container until the fire goes out due to insufficient oxygen. You then place some burning substance B in the container through an airlock. Are ...
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1answer
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Carbon emission in absence of oxygen [closed]

When wood is pyrolysed in absence of air is $\ce{CO2}$ emitted. If yes why is it not combustible?
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1answer
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What substances are hypergolic with liquid O2?

If something flammable is surrounded just by oxygen, I should see flame, right? The object would be even surrounded by more molecules than in the case of gas oxygen. On the youtube I see that people ...
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Does the ignition temperature of a substance decrease with the concentration of oxygen?

Is it possible for a substance to undergo combustion at a temperature lower than its ignition point if the concentration of oxygen increases?
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70 views

Computing the turbulent flame length

There is a problem I found online for practice that I cannot solve: Problem Methane, $\ce{CH4}$, emerges from a $1\ \mathrm{cm}$ diameter nozzle at a rate of $120\ \mathrm{cm^3/s}$ and a mole ...
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0answers
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Calorific values of biodiesels synthesized from vegetable oils

Calorific values of biodiesels vary depending on the feedstock used in synthesizing it. Although it's not by a lot, is there a particular reason for this? I suspect it's something to do with the ...
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1answer
339 views

Why do highly branched alkanes have higher octane numbers than their corresponding linear isomer?

The octane number of fuels are based on a set of primary reference fuels, which are mixtures of iso-octane and n-heptane. Now iso-octane being branched alkane has very less tendency to react and given ...
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0answers
32 views

Why fire spreads out, depending on burning substance, with different speed?

In Action movies, I have seen a couple of times that if flammable gases or liquids like benzene are ignited, the fire spreads out within fraction of a second and sometimes there is also an explosion. ...
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Is there the chemical component Hydrogen in Fire of any kind? [duplicate]

I know this sounds like a dumb question but I am wondering about the chemical composition of Fire, and it seems rather strange to me for the most part, is one of the compositions hydrogen since it ...
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1answer
77 views

Why are lower alcohols less flammable than their corresponding alkanes?

How to compare the general trend in amount of combustion in lower alcohols? (upto five/six carbons) Does the branching or straight chain have any effect on combustion?
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Heat of Combustion

Methanol ($\ce{CH3OH}$) is regarded by many chemists as a possible liquid fuel for the future. The combustion of methanol occurs according to the equation: $$\ce{2CH3OH(g) + 3O2(g) -> 2CO2(g) +...
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1answer
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Molar Heat of combustion with different fuels

I'm not sure exactly how to attack this question, I'm sure that you have to use equations such as $$Q=mc\triangle T$$ $$n=\frac{MM}{m}$$ But I don't know where to use them. Any help would be ...
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1answer
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Why doesn't this question violate the conservation of mass?

Combustion of of $0.255 \space g$ of isopropyl alcohol produces $0.561 \space g$ of $\ce{CO_2}$ and $0.306 \space g$ of $\ce{H_2O}$. Determine the emperical formula of isopropyl alcohol. I'm not ...
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1answer
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Why doesn't the carbon dioxide produced by a fire put out said fire?

Carbon dioxide ($\ce{CO2}$) is used in some fire extinguishers to put out fire, but a combustion reaction itself produces $\ce{CO2}$. Why do we get fire then? $$\ce{CH4 + O2 -> CO2 + H2O}$$ Why ...
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1answer
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More effective fire extinguisher liquid than water

I join robot fire fighting contest. One of the mission is to extinguish candle by spraying it with liquid (water is default option). For spray mechanism I use pump with Venturi effect principle. Is ...
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1answer
36 views

Polluting agents generated by road traffic in a city [closed]

I want to measure the air quality according to road traffic in a city. What are the polluting agents (generated by fuel combustion) strictly related and generated by road vehicles that is worth ...
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1answer
101 views

Can glucose burn in chlorine?

Chlorine is an oxidizing agent, so could it replace oxygen? If so, what would be the products, and how much energy would such reactions release? Do any other carbohydrates burn in chlorine? I cannot ...
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1answer
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Colored Flames Experiment

I am going to be doing a gender reveal for my sister's pregnancy. To do this, we wanted to light a huge fire pit and throw in a chemical to change the fire into the color (red/pink for girl, blue/...
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PM2.5 - result of compression ignition or Diesel fuel?

When reading about PM2.5 particles, one can see that one of the sources for such particulates is the Diesel engine. I was wondering if it is the Diesel fuel itself or is is the ignition type (i.e. ...
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1answer
27 views

Can the pyrophoric tendencies of a pyrophoric substance be suppressed in a pressurized environment?

It's common knowledge that the pressure of an environment influences many properties of a substance, like the melting point, boiling point, or triple point. Pyrophoric substances ignite spontaneously ...
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1answer
61 views

Combustion at 298K

Question: (source IITJEE 1992) An aliphatic thiol undergoes combustion at 298K to give carbon dioxide, water and sulfur dioxide. What are the physical states of the products?(solid/liquid/gas) I ...
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1answer
130 views

How can we separate carbon monoxide from wood gas?

I am thinking about using open source wiki designs from allpowerlabs to construct a wood gas generator. The motivation came from experiencing a 10 day power outage after super storm Sandy. The ...
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0answers
294 views

Reaction rate constants for methane combustion

I can't find a rate constant or activation energy for the methane combustion reaction given by: $$\ce{ CH4 + 2O2 -> CO2 + 2H2O}$$ Do all reactions have a rate constant? The NIST web site lists ...
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1answer
727 views

What chemical can cause such a fire? [closed]

A friend of mine who thinks that she is under influence of black magic met an astrologer. The astrologer asked her to wear a t-shirt for three nights and then bring that to him. The astrologer then ...
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1answer
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Can oxidation of hydrogen happen in room temperature? [duplicate]

Here is my explanation about the reaction between hydrogen or methane and oxygen. Hydrogen molecules and oxygen molecules can collide sucessfully and react if they have enough energy. In room ...
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1answer
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How do you work out the amount of energy which will be released when a substance undergoes combustion in a pure oxygen environment [closed]

For instance, if we have an abundance of pure Oxygen and one kilogram of Hydrogen and all the Hydrogen reacts with the Oxygen to form H20, how do you work out the amount of energy which will be ...