Angelica J.

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.

By: Tutor
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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?
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10/15/15 Christopher J.

Nothing. So the enthalpy change will be -967.2 kJ, and the correct answer is b).
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10/16/15

Joyce B.

I am convinced the enthalpy is -483.6
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03/10/18

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