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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About Smoke Grenades and Sugar Rockets

The most common formula for smoke grenades and sugar rocket fuel is $60\%\ \ce{KNO3}$ (potassium nitrate) and $40\%\ \ce{C12H22O11}$ (sugar). This is a 3:2 ratio, but I've also seen 2:1 and 5:3 with ...
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What Chemical Compounds Combust when Burning Coal & What is Coal Made of

My research suggests that when burning Coal to produce energy (or just burning coal in general), Carbon Dioxide is released into the other along with other gaseous chemicals. What other chemicals ...
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2answers
48 views

Rate law of the reaction of propane with oxygen

In class, I have a demonstration where I light a bubble filled with propane. As I add oxygen, the bubbles combust faster and more quickly. I have already balanced out the chemical reaction like so: $$...
3
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1answer
35 views

How to capture the gas produced by combusting alcohols

I am burning various alcohols and am attempting to capture the carbon dioxide produced. I could burn the alcohols in a conical flask with a cork on the top, with a tube directing the gas into a gas ...
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2answers
74 views

Complete combustion of mixtures

I am working on my scholarship exam practice (around high school and first year university level). I could actually solve the problem below but my solution is pretty time consuming. It would be ...
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1answer
35 views

Heat and work of glucose combustion

$$\ce{C6H12O6(s) + 6 O2(g) -> 6 CO2(g) + 6 H2O(g)}$$ When looking at glucose combustion I found that the change in Gibbs free energy is greater than the change in enthalpy. If we assume the process ...
7
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1answer
220 views

Based on their respective number of degrees of freedom, what's the most efficient fuel; hydrogen or gasoline?

The reaction of octane's combustion is: $$\ce{2 C8H18 + 25 O2 -> 18 H2O + 16 CO2}$$ I am asked for computing the number of degrees of freedom of the octane given that its specific heat is $\pu{...
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1answer
113 views

Redox Combustion Reactions

Consider a combustion reaction like the complete combustion of ethane. Here is what I have for the complete combustion as well as the oxidation and reduction: $$\ce{\overset{-3}{C}_2\overset{+1}{H}_6 ...
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2answers
6k views

When a candle burns, why does the top of wick glow if bottom of flame is hottest?

Totally an elementary question. Staring at a candle, it appears that the bottom of the wick is dark whereas the top glows. However the bottom of the flame (the blue) is the hottest. Is the reason ...
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0answers
19 views

Hydrogen peroxide and carbon as hybrid rocket propellant?

I was thinking that a hybrid rocket could be made using hydrogen peroxide and activated charcoal or some other carbon source. Step 1: Decompose hydrogen peroxide to steam and oxygen, as in a ...
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1answer
32 views

Does oxyhydrogen require the presence of water to ignite?

I recently read a short story (fiction) where a major plot element was based on the expectation that a mixture of oxygen and hydrogen will not ignite unless some amount of water is present to get the ...
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1answer
46 views

Why is the auto ignition temperature of petrol higher than that of diesel? [closed]

I can't find any reasonable explanation please help.
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2answers
80 views

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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0answers
35 views

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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0answers
37 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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2answers
72 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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0answers
35 views

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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0answers
77 views

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
127 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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60 views

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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0answers
57 views

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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0answers
37 views

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
151 views

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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6answers
6k views

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 ...
2
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1answer
56 views

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
140 views

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
35 views

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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2answers
409 views

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
90 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 ...
3
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1answer
93 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 ...
3
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1answer
571 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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1answer
155 views

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 ...
6
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2answers
409 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
39 views

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
58 views

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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0answers
43 views

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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0answers
74 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 ...
3
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1answer
575 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
34 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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1answer
112 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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1answer
129 views

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
54 views

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 $$Q=mc\,\Delta T$$ $$n=\frac{M}{m}$$ But I don't know where to use them. Any help would be ...
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1answer
36 views

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
95 views

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
63 views

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
39 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
117 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
811 views

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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1answer
32 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
69 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 ...