# Is Heat Capacity Derivable for Non-Ideal Liquid Mixtures?

• Gvozden
In summary, the conversation discusses the possibility of deriving the heat capacity of a one phase mixture of three liquids by using a sum of their mass shares multiplied by their individual heat capacities. However, it is noted that this method may not be accurate if the interaction parameters between the compounds cannot be ignored. It is also mentioned that a fourth component may be present due to the reaction between the two main liquids. It is ultimately advised to consult a properties program or conduct experimental measurements to determine the heat capacity of the mixture.
Gvozden
Can I derive heat capacity of one phase mixture of three liquids as a sum of their mass shares multiplied by heat capacities of solitary components at given temperature? All components are miscible, of course ... thank you in advance

You certainly can -- no one will stop you

In doing so, you make the assumption that the interaction parameters between the three compounds can be ignored. As a mixing rule, that is often good enough...

Gvozden and russ_watters
BvU, i could multiply the sum with Planck's constant, and still no one would stop me, wouldn't it? But it would make the result false.

As a matter of fact, third liquid serves as a cosolvent for two, otherwise non miscible liquids, changing two phase system into a single phase. Cosolvent does not participate in any kind of reaction, but there is a reaction between the other two liquids, thus only agitated by several types of intensification (microwave, ultrasound, laser, cavitation, conventional heating...)

Due to your response and advise, am I right to think that it is not advisable to calculate heat capacity like I asked to, and to measure heat capacity of the mixture by calorimetric bomb?

Ah, we are quickly exceeding my (nevertheless non-negligible) pay grade and have to call in some experts. @Chestermiller , for example.

Best advice I can give before starting bombing would be to consult a properties program like Aspen Properties (at least, if your components can be found there). Or dig around in the literature...

You can use the ideal mixing rule only for an ideal mixture. This is not an ideal mixture, as evidenced by the immiscibility of two of the components. So you are stuck measuring the heat capacity of the mixture experimentally. It sounds like if there is a chemical reaction, there is also going to be a 4th component present?

BvU

## What is heat capacity?

Heat capacity is the amount of heat energy required to raise the temperature of a substance by one degree Celsius or Kelvin.

## How is heat capacity calculated?

Heat capacity is calculated by dividing the amount of heat energy absorbed by the substance by the change in temperature.

## What units are used to measure heat capacity?

The most common unit used to measure heat capacity is joules per degree Celsius (J/°C) or joules per Kelvin (J/K). However, other units such as calories per degree Celsius (cal/°C) or British thermal units per degree Fahrenheit (BTU/°F) may also be used.

## What factors can affect the heat capacity of a substance?

The heat capacity of a substance can be affected by its mass, temperature, and molecular structure. Substances with a higher mass or more complex molecular structure tend to have a higher heat capacity.

## How is heat capacity related to specific heat?

Specific heat is the heat capacity per unit mass of a substance. In other words, it is the amount of heat energy required to raise the temperature of one gram of a substance by one degree Celsius. Specific heat is directly proportional to heat capacity, as both measure the ability of a substance to absorb heat.

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