Question

Chapter 12.1-12.4 Video 7 1. Define solute, solvent, and solubility. What are some possible units for solubility? 2. Define entropy. 3. Define dynamic equilibrium, saturated solution, unsaturated solution, and supersaturated solution. 4. Think about making a salt water solution (NaCl in H-0). What is the strongest IMF that exists in NaCI? What is the strongest IMF that exists between H:0 molecules? S. In order to create a solution Chink NaCI in HO) i) Solute-solute interaction: We must first break up NaCI (s) into Na* and Cr. Does this require or release energy? Is the AH for this process positive or negative? ii) Solvent-solvent interaction: We must then make space between H:0 molecules by overcoming the intermolecular forces that hold them close together. Does this require or release energy? Is the AH for this process positive or negative?

Answer 1

1. Solute: solute is a substance or component that is dissolved in another substance.

Solvent: solvent is that component in which the solute is dissolved.

Solubility: It is the property of a solute ( may be solid, liquid or gas) to get dissolve in a solvent.

Units of solubility:- It is often expressed as grams of solute per 100g of solvent. Other units are mol/L .

2) Entropy: It is represented as the degree of disorderness or randomness. It is defined as the thermodyanmic quantity which measures the unavailable energy in closed thermodynamic system.

3)Dynamic equilibrium is defined as a state of equilibrium in a continuing process( at a very fast rate) where the rate of forward reaction is equal to the rate of backward reaction.

Saturated solution is a homogeneous mixture which contains the maximum amount of the solute dissolved. Further solute added can't be dissolved.

Unsaturated solution is that solution where the solute concentarion is lower than the equilibrium concentration.

Supersaturated solution is that solution which contains more amount of solute than that could be dissolved .

4) The strongest IMF that exist in NaCl is the ionic force or the electrostatic force. The strongest IMF that exist in between the water molecules is the hydrogen bond.

5) (i) If we wish to break the bond between Na and Cl to get their ionic form then some energy is required. So ∆H is positive.

(ii) If we wish to break the solvent solvent interaction between the water molecules, then some energy is required. So ∆H is also positive for this process.

(iii) If a solute solvent interaction is made in between water and Na+ and Cl- , some energy is released in this process. ∆H is negative for the process. This process is called hydration and the IMF that exist in between water and the ions is ion- dipole interaction.

6) To make the overall process exothermic the negative ∆H must outweigh the positive ∆H value.

7) If ∆H of the solution is positive , the driving force is the solute-solvent interaction. That is the hydration of the ions or the ion dipole interaction.

8) on increasing the temperature ,solubility of a solid in liquid increases if the overall process is exothermic.

But the same is not true for gases dissolved in liquid. Their solubility decreases with increase in temperature.since increase in temperature causes increase in kinetic energy which in turn causes more molecules to escape from the solution.