C2H2(g)+ 5/2o2(g)-> 2Co2(g)+ H2o(g)+ 1255.8KJ

how many grams of C2H2 are reacted when 310 KJ of heat are released?

I left the oxygen (O) lowercase in the equation so it does not get mixed up with zero.

USUALLY we don't mix and o with an O. Placing a space, as in 5/2 O2 takes care of that possible mix up.

26 g C2H2 releases 1256.8 kJ.
26 g x (310 kJ/1255.8 kJ = ? g C2H2.

To find out how many grams of C2H2 are reacted when 310 KJ of heat is released, we need to use the given value of the energy change and the information about the chemical reaction.

First, let's convert the given energy change into Joules since most commonly used units are in Joules. 1 kJ = 1000 J.
So, 310 KJ = 310,000 J.

Given reaction: C2H2(g) + 5/2 O2(g) -> 2 CO2(g) + H2O(g) + 1255.8 KJ

The energy change (enthalpy change) in the reaction is -1255.8 KJ (negative because it is released).

Now, we need to set up a proportion to find the amount of C2H2 reacted.

We know that the energy change is proportional to the amount of C2H2 reacted. So, we can write the proportion as follows:

(310,000 J) / (unknown amount of C2H2 reacted) = (-1255.8 KJ) / (1 mole of C2H2 reacted)

We can simplify this by converting the energy change to joules and using the molar mass of C2H2:

Molar mass of C2H2 (acetylene) = 26.038 g/mol

Now, we can set up the proportion:

(310,000 J) / (unknown amount of C2H2 reacted) = (-1255.8 KJ) / (1 mole of C2H2 reacted)
(310,000 J) / (unknown amount of C2H2 reacted) = (-1255.8 * 1000 J) / (26.038 g C2H2)

To solve for the unknown amount of C2H2 reacted, cross-multiply and solve for it:

(310,000 J) * (26.038 g C2H2) = (-1255.8 * 1000 J) * (unknown amount of C2H2 reacted)
(310,000 J * 26.038 g C2H2) / (-1255.8 * 1000 J) = unknown amount of C2H2 reacted

Now, calculate the unknown amount of C2H2 reacted:

(310,000 * 26.038) / (-1255.8 * 1000) = unknown amount of C2H2 reacted

The calculated value will give you the grams of C2H2 reacted when 310 KJ of heat is released.