[Modar]

why does acetylene C2H2 gives 3000 degrees flame when burnt
hopefully the answer is detailed because i'm still in my start of studying chemistry
and sorry if my English is bad 

[TheUnassuming]

http://en.wikipedia.org/wiki/Heat_of_combustion

[Enthalpy]

Combined with the heat of combustion, a smaller heat capacity results in higher temperature. H₂O stores much heat, CO₂ less, CO even less.

As one goes to such temperatures, CO becomes predominant over CO₂, the heat of formation of the products accordingly smaller, and then the heat of formation of the fuel gets more important.

In the early days of rocketry, people tried things like N≡C-C≡C-C≡N, but they soon realized it had clear drawbacks  and didn't bring performance neither, because light product molecules are equally important there.

[Modar]

i know that it has a high heat of combustion value
the question is why ?
also i didn't understand why didn't people use Dicyanoacetylene N≡C-C≡C-C≡N , can u please explain it in simple way .

[TheUnassuming]

Are you asking why it has the specific heat of combustion it does? 

[TheUnassuming]

Or in other words, are you asking why it burns at X ºC as opposed to some other temp?

[Modar]

Are you asking why it has the specific heat of combustion it does? 

yes this is my question , and this can answer the second question ^_^

[Enthalpy]

i know that it has a high heat of combustion value
the question is why ?

Heat of formation of acetylene, due to the triple bond.
AND The small heat capacity of the flame products makes it hotter.

also i didn't understand why didn't people use Dicyanoacetylene N≡C-C≡C-C≡N , can u please explain it in simple way .

Boom.

[Modar]

boom  this rally simple

[Modar]

still no detailed answers?

[zsinger]

Here goes:
Triple bond has more energy as a double which has more energy as a single.  When we crack this hydrocarbon, the δH is HUGE.  Thats really all there is to it.  Imagine it this way.  Carbohydrates have a carbon-hydrogen bond which is broken, turned to ATP, and utilized for energy.  Same thing here, except the carbon-hydrogen bond is much more energetic, and when the triple bond is broken, MUCH heat is attained.  An obvious exothermic reaction once an ignition source has been added .
               -Zack

[zsinger]

Enthalpy-
My thoughts EXACTLY lol!!!!!!!