solution_part2.p pt CHEMISTRY CLASS 12

SOLUTION

1. SOLUTIONS
CONCEPT MAP
•Method of expressing the concentration of the
solution: molarity , molality , mole fraction , parts per
million.
•Solubility of solid in liquid , solubility of gas in liquid.
•Raoult’s law , ideal and non-ideal solution
•Colligative properties: Relative lowering of vapour
pressure , elevation in boiling point , depression in
freezing point , osmotic pressure
•Abnormal molecular mass , Van’t hoff factor

2. Saturated Solutions
We can add solute to a
solvent until NO more solid
will dissolve to form a
Saturated Solution
•Saturation defines the
solubility of the solute
•Solubility is the maximum
amount of solute that can be
dissolved in a given solvent

3. Solubility is based on:
1.Pressure applied to the system
2.Temperature of the solution
3.Nature of the solvent and solute interaction
Solubility

4. Solubility of solid in liquid
Factors affecting solubility of solid in liquid
1. Nature of the solute and solvent: polar solute dissolve in polar solvents and non-
polar solute dissolve in non polar solvent.
2. Effect of temperature : If the dissolution process is exothermic , the solubility
decreases with temperature(according to the Le Chatelier’s principle)
solute + solvent  solution +Heat
If the dissolution process is endothermic , the solubility increases with
temperature(according to the Le Chatelier’s principle)
solute + solvent + Heat  solution

5. Attractive Forces in Solutions
Interactions between solutes and solvents that:

•are similar in polarity will form a solution

•are not similar will not form a solution
“Like dissolves like”

6. Solubility of gas in a liquid
1.Effect of pressure: Henry’s law states that ; the partial pressure of the gas in vapour phase is
proportional to the mole fraction of the gas in the solution

Higher the value of KH at a given pressure , the lower is the solubility of the gas in
liquid.

8. 2. Effect of temperature : As dissolution of gas in
liquid is always exothermic in nature , therefore according to the
Le Chatelier’s principle , the solubility should decreases with
increases of temperature.
Gas + liquid  solution + Heat
This is the reason that aquatic species are more comfortable in
cold water rather than in warm water.

9. Questions
1. State and explain Henry’s Law.
2. Mention two application of Henry’s Law.
3. Explain why aquatic species are more comfortable in cold water rather than

in cold water.
4. Gas(A) is more soluble in water than gas (B) at the same temperature .
Which one of the two gases will have higher value of Henry’s constant.
5. N2 and O2 gases have KH values 76.48 kbar and 34.86 kbar respectively at 293 K
temperature. Which one of these will have more solubility in water?
6. . Given reason for the following :–
(a) To avoid bends scuba divers use air diluted with helium.
(b) Cold drinks bottles are sealed under high pressure
7. If O2 is bubbled through water at 393 K how many millimoles of O2 gas would be
dissolved in 1L of water? Assume that O2 exerts a pressure of 0.95 bar. (Given KH for
O2 = 46.82 bar at 393K).
8. Why gases tends to be less soluble at higher temperature?