Amount Of Energy Produced When Methane Is Combusted To Form Water
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Amount Of Energy Produced When Methane Is Combusted To Form Water

The combustion of 1 molecule of methane gas has water as a product:
(a) Calculate the amount of energy produced during this reaction.
(b) A typical X-ray photon has an energy of 8eV. How does the energy produced in(a) compare to the energy of the X-ray photon?

The strings: S7P6A66 (grouping/interaction - chemical).

The math:
Pj Problem of Interest is of type grouping/interaction (chemical).

(a) The balanced chemical equation is:

CH4(g) + 2O2(g) -------> CO2(g) + 2H2O(l)

ΔH0reaction = ΣnΔH0f(products) - ΣmΔH0f(reactants)
Where ΔH0 = standard enthalpy change at standard pressure (1 atm) and temperature 250C (298 K).
ΔHf = enthalpy of formation
n is coefficients of products and m is coefficients of reactants.

Enthalpy Of Formation From Enthalpy Table:
ΔH0f of CH4 = -74.80 kJ
ΔH0f of O2 = 0 (since this is the most stble state of oxygen)
ΔH0f of CO2 = -393.5 kJ
ΔH0f of H2O = -285.8 kJ
From Equation:
ΔH0reaction = -393.5 -2(285.8) - (-74.8) = -965.1 + 74.8 = -890.4 kJ.
So 890.4 kJ of energy is released when 1 mole of CH4 is combusted
1 mole contains 6.022 x 1023 molecules (Avogadro's number)
So, energy released from combustion of 1 molecule of CH4(g) = (890.4)/(6.022 x 1023) = 1.479 x 10-18 J/molecule.

(b) 1eV = 1.602 x 10-19 J
So, 8eV = 8(1.602 x 10-19) = 1.2 x 10-15 J/photon
So, the energy from a photon of X-ray is 1000 times more than that produced from the combustion of 1 molecule of CH4(g).

Math

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