# Lattice energy, hydration energy, solution energy

• MHB
• WMDhamnekar
In summary, lattice energy is the energy released during the formation of ionic compounds from their constituent ions in the gas phase. It is calculated using the Born-Haber cycle and is a measure of the strength of ionic bonds in a crystal lattice. Hydration energy, on the other hand, is the energy released when ions are surrounded by water molecules in a solution and is a measure of the strength of ion-dipole interactions. It plays a significant role in determining the solubility of ionic compounds in water. Lastly, solution energy is the overall energy change that occurs when a solute dissolves in a solvent and takes into account both the lattice energy and the hydration energy of the ions in solution.
WMDhamnekar
MHB
Hi,

The enthalpy of crystallization of $KCl$ (Potassium Chloride) is + 715 kJ/mol. The enthalpies of hydration for Potassium and Chloride are -322 and -363 kJ/mol respectively. So, enthalpy of solution of $KCl \Delta H_{sol}=\Delta H_{lattice} - \Delta H_{hyd}$

$\Delta H_{sol}=715 kJ/mol -685 kJ/mol= 30 kJ/mol.$

But if you see table of enthalpy of solution, it is -17.22 kJ/mol for $KCl(s).$ Obviously, our experiment value 30 kJ/mol indicates dissolving $KCl$ into water is endothermic reaction. Should the temperature increase or decrease when $KCl$ dissolves?

My answer is temperature increase when $KCl$ dissolves.

What types of interaction are present when $CaCl_2$ dissolves in ethanol($CH_3CH_2OH)$?

What is the major type of interaction when toluene$C_7H_8$ dissolves in benzene$C_6H_6?$

Which ion has a larger absolute value of enthalpy of hydration, $Na^+$ or $Ca^{2+}$?
My answer: $Ca^{2+}$

Which ion is larger, $Na^+$ or $Cl^-?$
My answer is $Cl^-$

When $KNO_3$ is dissolving in water, will the temperature decrease or increase?

Dhamnekar Winod said:
Hi,

The enthalpy of crystallization of $KCl$ (Potassium Chloride) is + 715 kJ/mol. The enthalpies of hydration for Potassium and Chloride are -322 and -363 kJ/mol respectively. So, enthalpy of solution of $KCl \Delta H_{sol}=\Delta H_{lattice} - \Delta H_{hyd}$

$\Delta H_{sol}=715 kJ/mol -685 kJ/mol= 30 kJ/mol.$

But if you see table of enthalpy of solution, it is -17.22 kJ/mol for $KCl(s).$ Obviously, our experiment value 30 kJ/mol indicates dissolving $KCl$ into water is endothermic reaction.

I'm seeing slightly different numbers from different sources and I'm not sure why.
Either way, with your numbers it takes 715 kJ/mol to break the lattice, and 685 kJ/mol is released when we dissolve the ions.
The result is positive, meaning that it takes energy to dissolve $\ce{K Cl}$, which is indeed endothermic.

Should the temperature increase or decrease when $KCl$ dissolves?
My answer is temperature increase when $KCl$ dissolves.

It takes energy to dissolve the crystal, which must come from somewhere.
It means that the temperature will decrease instead of increase.

What types of interaction are present when $CaCl_2$ dissolves in ethanol($CH_3CH_2OH)$?
Correct.

What is the major type of interaction when toluene$C_7H_8$ dissolves in benzene$C_6H_6?$

Which ion has a larger absolute value of enthalpy of hydration, $Na^+$ or $Ca^{2+}$?
My answer: $Ca^{2+}$

Which ion is larger, $Na^+$ or $Cl^-?$
My answer is $Cl^-$

You didn't explain why... but yeah, that looks correct to me.

When $KNO_3$ is dissolving in water, will the temperature decrease or increase?

It appears that $\ce{K NO3}$ also has a positive enthalpy of solution.
It means that the temperature will decrease as well since it takes energy to dissolve.

## 1. What is lattice energy?

Lattice energy is the energy released when ions in a solid crystal lattice come together to form a compound. It is a measure of the strength of the ionic bonds in a compound.

## 2. How is lattice energy calculated?

Lattice energy is calculated using the Born-Haber cycle, which takes into account the formation of the compound from its constituent elements and the energy required to break the ionic bonds in the crystal lattice.

## 3. What is hydration energy?

Hydration energy is the energy released when ions in a crystal lattice are surrounded by water molecules in a solution. It is a measure of the strength of the ion-dipole interactions between the ions and water molecules.

## 4. How does hydration energy affect solubility?

The stronger the hydration energy of an ion, the more likely it is to dissolve in water. This is because the energy released from hydration can overcome the energy required to break the ionic bonds in the crystal lattice, allowing the compound to dissolve.

## 5. What is solution energy?

Solution energy is the overall energy change that occurs when a solute dissolves in a solvent. It takes into account both the lattice energy of the solute and the hydration energy of the ions in solution.

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