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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415 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 ...
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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 ...
4
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1answer
455 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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3answers
398 views

Open flame combustion in bizarro world

Humans typically achieve combustion by starting a chemical reaction of a fuel (often a carbon $\ce{C}$ containing fluid like methane $\ce{CH4}$), which is is brought into an an oxidizer (a gas ...
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1answer
646 views

What are the key chemical characteristics that determine the octane rating of fuel?

The octane rating of petrol (gasoline) is a measure of the how much compression a fuel air mixture can have before detonating (which in petrol engines is a bad thing as you want the mix to combust ...
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50 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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6answers
8k 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 ...
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3answers
1k views

Why can wood burn all the way to charcoal instead of just creating a passivating charcoal layer?

I know burning to charcoal is actually incomplete combustion because charcoal can also burn. When a strike anywhere match burns, it burns all the way to charcoal but the charcoal doesn't further burn. ...
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1answer
1k views

Why does burning wood produce methane and other hydrocarbon chains?

This post kinda helps me understand and it sounds like it has to do with pyrolysis, but I'm having trouble putting the exact reactions together.
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1answer
327 views

Gases produced by pyrolysis of cellulose

I heated cotton in a sealed container (with a small hole) over a natural gas flame. Some gases and smoke were produced. What would they probably be? I can come up with some guesses based on the ...
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3answers
838 views

What really happens atomically in an explosion?

Let's say a room is filled with butane, I then throw a cigarette into the room. What happens to the atoms/molecules of the butane when they are in contact with the heat from the cigarette?
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2answers
448 views

What are the major environmental drawbacks with using methane as a combustable fuel?

What are the biggest environmental issues with using methane, $\ce{CH4}$, (which is found as the major energy source in natural gas, shale gas, biogas, and synthetic natural gas), as a combustible ...
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2answers
786 views

Spectrometry in Chemistry & Flame Test Lab

Question 1: You currently see two colors that are two similar (dark yellow and orange) in a flame test lab. And also you have a hard time differentiating the colors, what is an alternative to ...
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1answer
9k views

Why is there sulfur in black powder / gun powder?

Black powder is composed of charcoal, sulfur and a nitrate salt. The charcoal and sulfur serve as fuel and the nitrate is the oxidizing agent. However, wouldn't it be cheaper to leave out the sulfur, ...
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3answers
362 views

Why does internal combustion engine smoke appear blue? Could there be “blue molecules” in it?

Four-stroke and two-stroke gasoline engines as well as diesel engines can all emit dense clouds of blue-tinged smoke under various transient loads or incorrectly tuned conditions. Raleigh scattering -...
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1answer
200 views

What proportion of a combustion engine's output energy comes from the air?

When trying to compare the efficiency and range of electric engines vs gasoline engines, it seemed at first that gasoline had a higher energy density than batteries. But then I realiced that a ...
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1answer
45 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
1k 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
404 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
59 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 (...
135
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7answers
41k views

Why doesn't water burn?

Hydrogen is flammable, and for any fire to burn it needs oxygen. Why does a compound made of hydrogen and oxygen put out fires instead of catalyzing them? I understand that hydrogen and water are ...
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2answers
984 views

How to calculate the amount of substances product produces from the masses and amounts of starting materials?

Calculate the amount of carbon dioxide formed when we burn 1 mole of carbon in the presence of 16 g of dioxygen. $$\ce{C + O2 -> CO2}$$ 1 mole of carbon means 12 g. Therefore amount of ...
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4answers
3k views

Does any known substance ignite on cooling?

As the title says, I'm interested in knowing if there is any substance — or combination of substances — that ignites (or even increases its chance of spontaneous ignition) when cooled. I've never ...
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2answers
97 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
51 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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1answer
1k views

What defines incomplete combustion?

I know that complete combustion is a process where a fuel reacts with $\ce{O2}$ to become $\ce{CO2}$ and $\ce{H2O}$. But what is incomplete combustion? According to the Internet, $\ce{CH4 + O2}$ and ...
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0answers
80 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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2answers
8k views

What product will be produced when a sucrose and potassium nitrate mix burns? [closed]

What product will be obtained get when a sucrose and potassium nitrate mix, which are the ingredients for smoke bomb, are burned in a combustion container? $$\ce{KNO3 + C12H22O11 -> ?}$$
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1answer
385 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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2answers
8k views

Why is the smell of car exhaust much stronger in winter?

I noticed that in winter, the smell of cars (to be precise the smell of the exhaust gases) is much stronger in winter. I just can't figure out why. Has this got something to do with the air ...
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0answers
270 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
59 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
66 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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2answers
180 views

Are all highly shock sensitive chemicals highly temperature sensitive too?

I found that some highly shock sensitive explosives like lead azide, mercury fulminate have a relatively high auto-ignition temperature. I want to know if it's a general property or not and why so? ...
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2answers
3k views

How can titanium burn in nitrogen?

I was going through the properties of titanium when a certain thing caught my eye: It was the reaction of burning of titanium in nitrogen. I was astonished to read it as I knew that neither is ...
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1answer
68 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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2answers
2k views

Why should fire extinguishers containing carbon dioxide not be used on magnesium fires?

As the title states, why should $\ce{CO2}$ fire extinguishers containing carbon dioxide not be used on fires with magnesium metal? I understand that $\ce{CO2}$ extinguishers work by displacing oxygen,...
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4answers
2k views

Would the concentration of oxygen around fire increase as we get close to the fire (from the outside)

Since fire require oxygen, wouldn't a fire, like those in the American forest along west coast, constantly draws in oxygen from around? And if that is so, would the concentration of oxygen around the ...
9
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1answer
7k views

Why do gummy bears explode when added to hot potassium chlorate?

This link shows that a gummy bear explodes when in contact with heated potassium chlorate, $\ce{KClO3}$. But what in a gummy bear creates this reaction? Also, do other foods (fruit, icing sugar...) ...
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3answers
155 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
61 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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1answer
227 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
905 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
354 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 ...
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3answers
4k views

How do you melt magnesium without causing its combustion?

How do you melt magnesium without causing its combustion? I own a foundry capable of reaching temperatures around 2000 °F, and I recently bought some magnesium for melting before doing my ...
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0answers
188 views

Which (carbonaceous) fuels produce more or less soot in a diffusion flame, and how to predict that?

From what I've read, the production of soot in a flame is still an open research topic. But some hydrocarbon fuels produce much more soot than others. Are there (simple) rules that tell which fuels ...
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2answers
438 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 ...
3
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1answer
789 views

Mechanics behind auto-ignition temperature

I have some questions about the auto-ignition temperature for fuels. Per ASTM E659: AIT (auto-ignition temperature) is the lowest temperature at which the substance will produce hot-flame ignition ...
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1answer
41 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
15k views

Calculate the mass of butane gas that would be needed to heat 724 cm³ of water from an initial temperature of 7.44 °C to 50.7 °C [duplicate]

The thermochemical equation for the combustion of butane is: $$\ce{2C4H10(g) + 13O2(g) -> 8CO2(g) + 10H2O(l)} , \quad\Delta H = -5748 \ \mathrm{kJ\cdot mol^{−1}}$$ So far, I've calculated the heat ...

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