Question

Calculate the enthalpy change when 4.00 mol Cl2O7 is produced according to the following balanced equation:

2Cl2(g) + 7O2(g) + 130kcal -> 2Cl2O7(g)
a. 1040 kcal
b. -260 kcal
c. 260 kcal
d. -1040 kcal

** if you could explain it as well, that would be much appreciated !! if not, thats okay too its multiple choice

Answer 1

So the equation is,

2Cl2(g) + 7O2(g) + 130kcal -> 2Cl2O7(g)

from this , ΔH°rxn=
`130kcal.mol^(-1)`

`mol^(-1)` is mentioned because it is for per mole of reaction. So for 4. moles of the product
`2Cl_(2) O_(7)` we need 4/2 moles of reaction to be used to calculate associated enthalphy change for the reaction.

Therefore
`4/2*130=260 kcal`