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

Question

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. 

Answer 1

You are producing twice as much water in the second reaction equation as you made in the reference reaction equation.

So do you think you produce (release) twice as much energy, or the same amount of energy? Also, the value for the enthalpy change in the reference reaction equation is negative. So in producing twice as much water, do you think the change in enthalpy in the second equation will also be negative, or will it be positive?