A, They Lower The Activation Energy.
Answer : The energy of the photon emitted is, -12.1 eV
Explanation :
First we have to calculate the
orbit of hydrogen atom.
Formula used :

where,
= energy of
orbit
n = number of orbit
Z = atomic number of hydrogen atom = 1
Energy of n = 1 in an hydrogen atom:

Energy of n = 2 in an hydrogen atom:

Energy change transition from n = 1 to n = 3 occurs.
Let energy change be E.

The negative sign indicates that energy of the photon emitted.
Thus, the energy of the photon emitted is, -12.1 eV
Answer:
C8H18(g) + 12.5O2(g) -> __8__CO2(g) + 9H2O(g) + heat
CH4(g) + _2___O2(g) -> ____CO2(g) + _2___H2O(g) + heat
C3H8(g) + _5___O2(g) -> _3___CO2(g) + __4__H2O(g) + heat
2C6H6(g) + __15__O2(g) -> __12__CO2(g) + __6__H2O(g) + heat
Explanation:
I hope it helps!
There would be 2 which would be on the oxygen