The combustion of petrol can be approximately represented by the

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In summary, the conversation discussed the combustion of petrol represented by the equation 2C8H18(g) + 25O2 -----> 16CO2 + 18H2O and the density of octane which is 0.7 gcm^{}-3. The question was how much oxygen is used up when 1L of petrol is burnt in a car engine. The summary included calculations using the density of octane and the molar mass of oxygen to determine the amount of oxygen used, which was found to be 2.5*10^3 grams. There was some confusion about the mol ratio and whether to multiply by 25 or 12.5, but ultimately the correct answer was reached.
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The combustion of petrol can be approximately represented by the equation

2C8H18(g) + 25O2 -----> 16CO2 + 18H2O

The density of Ocatane is 0.7 gcm(cubed)

What mass of oxygen is used up when 1L of petrol is burnt in a car engine?

ATTEMPT

0.7 gcm[tex]^{}-3[/tex] = 0.0007 gL[tex]^{}-1[/tex]
Therefore
density = mass/volume
0.0007 gL[tex]^{}-1[/tex] = mass / 1 L
0.0007g = mass

amount (of petrol) = mass/molar mass
= 0.0007/228
= 0.000003 mols

therefore...amount of oxygen is 25 times amount i got for petrol?
so
n(o) = 0.000003*25
then
0.000075 = mass/molar mass
0.000075 = mass/32
0.0024g = mass


Have i blown it somewhere? I am not sure about the mols thing i did when going from petrol to oxygen... I mean do you times it by 25 OR 12.5 because the mol ratio is 2petrol + 25Oxygen
i think times by 25 because when finding molar mass for petrol I multiplied everything by 2

btw the right answer is appparentlyyyy 2.5*10^3 grams, what did i do? ahh
cheers
 
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  • #2


Mass of 1L is not 0.0007g.

Please use [noparse]cm3[/noparse] tags for cm3 and [noparse]H2[/noparse] for H2.
 

Related to The combustion of petrol can be approximately represented by the

1. What is the chemical reaction behind the combustion of petrol?

The combustion of petrol is a chemical reaction that involves the breaking down of the hydrocarbon molecules in petrol (C8H18) into smaller molecules of carbon dioxide (CO2) and water (H2O) in the presence of oxygen (O2). This reaction releases energy in the form of heat and light.

2. Why is petrol considered a good fuel for combustion?

Petrol is considered a good fuel for combustion because it has a high energy density, meaning it contains a large amount of energy per unit of volume. It also vaporizes easily and is highly flammable, making it easy to ignite and burn efficiently.

3. How does the combustion of petrol power engines?

The combustion of petrol powers engines by converting the chemical energy in petrol into mechanical energy. This is achieved through a series of controlled explosions in the engine's cylinders, which drive the pistons and ultimately turn the engine's crankshaft.

4. Is the combustion of petrol a complete or incomplete combustion process?

The combustion of petrol is a complete combustion process, meaning that all of the fuel is burned and converted into carbon dioxide and water. This is because petrol contains a sufficient amount of oxygen to allow for complete combustion to occur.

5. What are the byproducts of the combustion of petrol?

The byproducts of the combustion of petrol are carbon dioxide (CO2) and water (H2O), as well as small amounts of other gases such as carbon monoxide (CO) and nitrogen oxides (NOx). These byproducts are released into the atmosphere and contribute to air pollution and the greenhouse effect.

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