Angelica J.

asked • 10/15/15

Calculate enthalpy change for a reaction?? PLEASE help????????

The enthalpy change for the following reaction is -483.6 kJ:

2H2 (g) + O2 (g) → 2H2O (g)

Therefore, the enthalpy change for the following reaction is __________ kJ:

4H2 (g) + 2O2 (g) → 4H2O (g)
a. 483.6
b. -967.2
c. 967.2
d. 2.34 x 10^5
e. -483.6
I think it is b, since it seems that since the equation was just multiplied by two, the enthalpy would also be multiplied by 2. (2 * -483.6) = -967.2
I don't know if this is right though. I am consistently getting thrown off by how to determine whether answers should have positive or negative H's. 

1 Expert Answer


Christopher J. answered • 10/15/15

4.8 (158)

Math, Chemistry, Physics, SAT & Computer Programming Tutor

Angelica J.

Thank you for the reply! I think I would produce twice as much energy, since energy is an extensive property. however, if I am just producing twice as much energy, what would cause the enthalpy change to be positive? 


Christopher J.

Nothing. So the enthalpy change will be -967.2 kJ, and the correct answer is b).


Joyce B.

I am convinced the enthalpy is -483.6


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