Molar Enthalpy of Salt: Calculation and Heat Sources

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In summary, the conversation discusses testing three different salts (NH4Cl, KN03, and LiCl) in a lab and finding their respective heats and molar enthalpies. There is a question about whether to use the mass of just the water or the mass of the water and salt when calculating heat using the equation mcΔt. The speaker also clarifies that using specific heat capacity of the solution, rather than just water, is more accurate for diluted solutions.
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Hannah Wallace
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Please post this type of questions in HW section using the template.
So for a lab I had to test three different salt Nh4Cl,KN03 and LiCl. I found the heat of each of them and then in turn found the molar enthalpy by using N*molar enthalpy=-heat. When finding my heat and using equation mcΔt would I use the mass of the water or the mass of the water and the salt?
 
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Note: things like "heat", "enthalpy" are properties of a process, not of a substance, so what you wrote doesn't make much sense. I guess what you mean is "heat of dissolution" and "enthalpy of dissolution" (AKA "heat/enthalpy of solution").

Mass of water and salt is a bit more correct, although technically you should also use specific heat capacity of the solution, not of the pure water. For diluted solutions using specific heat capacity of water is usually accurate enough.
 

1. What is the molar enthalpy of salt?

The molar enthalpy of salt is the amount of heat energy absorbed or released when one mole of salt is dissolved in water. It is typically measured in units of kilojoules per mole (kJ/mol).

2. How is the molar enthalpy of salt calculated?

The molar enthalpy of salt can be calculated using the equation ΔH = Q/m, where ΔH is the change in enthalpy (in kJ), Q is the heat energy absorbed or released (in J), and m is the number of moles of salt. This calculation can be done experimentally or using thermodynamic data.

3. What factors affect the molar enthalpy of salt?

The molar enthalpy of salt is affected by the type of salt being dissolved, the temperature of the solution, and the concentration of the salt. The presence of any impurities in the salt can also affect the molar enthalpy.

4. What are the heat sources for the molar enthalpy of salt?

The heat sources for the molar enthalpy of salt can include exothermic reactions, such as the dissolution of an ionic salt, and endothermic reactions, such as the dissociation of a covalent salt. In addition, changes in temperature and phase transitions can also contribute to the overall heat energy of the system.

5. How is the molar enthalpy of salt used in real-world applications?

The molar enthalpy of salt is used in various industries, such as pharmaceuticals, food and beverage, and chemical manufacturing. It is also used in environmental studies, such as in the calculation of the energy released during the mixing of saltwater and freshwater in estuaries. Additionally, understanding the molar enthalpy of salt is important in designing and optimizing processes for salt production and purification.

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