# Calculating heat released from excess enthalpy

• rwooduk
In summary, excess enthalpy, also known as heat of mixing, is the amount of heat released or absorbed when two or more substances are mixed together. To calculate the heat released from excess enthalpy, the equation Q = mCΔT can be used, where Q is the heat released, m is the mass of the mixture, C is the specific heat capacity, and ΔT is the change in temperature. This calculation is important in understanding energy changes during mixing, predicting temperature changes, and determining the feasibility of a chemical reaction. The heat released from excess enthalpy can be affected by the types and amounts of substances, as well as the temperature and any other reactions or processes in the system. However, one limitation
rwooduk
Hello,

I am currently trying to determine the method to calculate the heat absorbed / released when a gas and liquid mix. I believe that this is known as the heat/enthalpy of mixing (or excess molar enthalpy). I also believe, that if this value is negative it means an exothermic reaction (heat released), if the value is positive it means an endothermic reaction (heat absorbed).

I'd really appreciate some direction on where to go from here. How would I calculate the actual heat absorbed/released from the heat of mixing value.

Thanks for any help.

Hello,

Calculating the heat released from excess enthalpy can be done using the following equation:

Q = nΔH

Where Q is the heat released, n is the number of moles of the substance involved, and ΔH is the change in enthalpy (in joules/mol).

To calculate the excess molar enthalpy, you will first need to determine the initial and final enthalpy values for the gas and liquid mixture. This can be done by using the heat capacity and temperature of each component.

Once you have these values, you can use the equation:

ΔH = Hfinal - Hinitial

Where ΔH is the change in enthalpy, Hfinal is the final enthalpy value, and Hinitial is the initial enthalpy value.

If the resulting ΔH value is negative, it means that the reaction is exothermic and heat is released. If the value is positive, it means that the reaction is endothermic and heat is absorbed.

To calculate the actual heat released or absorbed, you will need to know the amount of substance involved (in moles). You can then use the first equation mentioned to determine the heat released or absorbed.

I hope this helps. If you need more specific guidance, I suggest consulting a textbook or reaching out to a chemistry tutor for further assistance. Good luck!

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