# How do you find the enthalpy change?

The equation

H2 (g) + Cl2 (g) --> 2HCl (g) has the enthalpy change of -185kJ.

So, if I want to find the enthalpy change for the following reaction:

6HCl (g) --> 3H2 (g) + 3Cl2 (g),

do I multiply +185kJ by 3? I know that the equation is reversed, so the enthalpy change should be positive...but do you multiply by 3, since the products of the original equation is tripled in the reactant of the second equation?

Yes, if the original reaction is multiplied by some number, you multiply the enthalpy change by the same number. You are correct in reversing the sign on the enthalpy change as well since the reaction is going in the reverse direction.

Yes.

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H2 (g) + Cl2 (g) --> 2HCl (g) has the enthalpy change of -185kJ.

So, if I want to find the enthalpy change for the following reaction:

6HCl (g) --> 3H2 (g) + 3Cl2 (g),

do I multiply +185kJ by 3? I know that the equation is reversed, so the enthalpy change should be positive...but do you multiply by 3, since the products of the original equation is tripled in the reactant of the second equation?

**Answer:**Yes, if the original reaction is multiplied by some number, you multiply the enthalpy change by the same number. You are correct in reversing the sign on the enthalpy change as well since the reaction is going in the reverse direction.

Yes.

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