Is Dissolution of LiNO3 in Water Exothermic?

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In summary: Just be careful with units. The standard enthalpy of formation is usually given in kJ/mol, not KJ/mol.
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Mitchtwitchita
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When LiNO3 dissolves in water, the enthalpy of solution is -2.5 KJ/mol. The standard enthalpy of formation of solid LiNO3 is -483.1 KJ/mol.
(a)When LiNO3 dissolves in water, is the dissolution endothermic or exothermic?
(b)Will the solubility of LiNO3 increase or decrease as the temperature increases?
(c)Calculate the standard enthalpy of formation (KJ/mol) for aqueous LiNO3.

(a)The process would be exothermic because the enthalpy of solution is -2.5 KJ/mol

(b)The solubility would increase because the solubility of every nitrate salt I've seen increases with an increase in temperature. Also, the solubility of most salts in general increase with an increase in temperature.

(c)I'm pretty lost on this one.

Li+ + NO3- ---> LiNO3 delta Hrxn = -483.1 KJ/mol
LiNO3 + H2O ---> Li+(aq) + NO3-(aq) delta Hsoln = -2.5 KJ/mol

= -485.6 KJ/mol?

Any help with this one would be appreciated!
 
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Mitchtwitchita said:
(a)The process would be exothermic because the enthalpy of solution is -2.5 KJ/mol
Yes.

Mitchtwitchita said:
(b)The solubility would increase because the solubility of every nitrate salt I've seen increases with an increase in temperature. Also, the solubility of most salts in general increase with an increase in temperature.
No. This is an illustration of Le Chatelier's principle. Your equilibrium equation goes like this:
$$\mathrm{LiNO_{3(s)}} \rightleftharpoons \mathrm{Li^+_{(aq)}} + \mathrm{NO_{3(aq)}^{-}} + \mathrm{heat}$$
Increasing the temperature adds heat which, following Le Chatelier, will push the equilibrium toward solid LiNO3. So increasing temperature decreases solubility of this salt.

Mitchtwitchita said:
(c)I'm pretty lost on this one.

Li+ + NO3- ---> LiNO3 delta Hrxn = -483.1 KJ/mol
LiNO3 + H2O ---> Li+(aq) + NO3-(aq) delta Hsoln = -2.5 KJ/mol

= -485.6 KJ/mol?
This looks fine.
 

Related to Is Dissolution of LiNO3 in Water Exothermic?

1. What is the definition of heat of solution?

The heat of solution refers to the amount of heat released or absorbed when a substance dissolves in a solvent to form a solution.

2. How is heat of solution measured?

Heat of solution is typically measured in units of joules per mole (J/mol) or kilojoules per mole (kJ/mol) using a calorimeter, which is a device that measures the heat exchanged during a chemical reaction.

3. What factors affect the heat of solution?

The heat of solution is affected by the nature of the solute and solvent, as well as the temperature and pressure of the system. Generally, substances with stronger intermolecular forces will have a higher heat of solution, while higher temperatures and pressures can increase the solubility of a substance and thus affect its heat of solution.

4. How does the heat of solution relate to enthalpy?

Enthalpy is a measure of the total energy of a system, including the heat exchanged with the surroundings. The heat of solution is a specific type of enthalpy change, specifically the enthalpy change associated with the formation of a solution.

5. What are some practical applications of understanding heat of solution?

Understanding the heat of solution can be useful in various industries, such as pharmaceuticals, where the solubility of a drug can affect its effectiveness. It is also important in the production of various solutions, such as fertilizers, detergents, and food products. Additionally, the heat of solution plays a role in the dissolution of minerals in soil, which can impact plant growth and agricultural practices.

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