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Solutions.

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Presentation on theme: "Solutions."— Presentation transcript:

1 Solutions

2 Solutions An electrolyte is a substance that dissociates into ions when dissolved in water. A nonelectrolyte may dissolve in water, but it does not dissociate into ions when it does so. © 2012 Pearson Education, Inc.

3 Dissociation When an ionic substance dissolves in water, the solvent pulls the individual ions from the crystal and solvates them. This process is called dissociation. solvation © 2012 Pearson Education, Inc.

4 Dissociation An electrolyte is a substances that dissociates into ions when dissolved in water. © 2012 Pearson Education, Inc.

5 Electrolytes and Nonelectrolytes
Soluble ionic compounds tend to be electrolytes. © 2012 Pearson Education, Inc.

6 Electrolytes and Nonelectrolytes
Molecular compounds tend to be nonelectrolytes, except for acids and bases. © 2012 Pearson Education, Inc.

7 Electrolytes A strong electrolyte dissociates completely when dissolved in water. A weak electrolyte only dissociates partially when dissolved in water. © 2012 Pearson Education, Inc.

8 Double replacement Reactions
Must start with 2 compounds The cation from one compound and the anion from the other will form a new compound AgNO3(aq) + KCl(aq)  AgCl(s) + KNO3(aq) © 2012 Pearson Education, Inc.

9 Double replacement Reactions
It appears as though the ions in the reactant compounds exchange, or transpose, ions: AgNO3(aq) + KCl(aq)  AgCl(s) + KNO3(aq) © 2012 Pearson Education, Inc.

10 Precipitation Reactions
When one mixes ions that form compounds that are insoluble (as could be predicted by the solubility guidelines), a precipitate is formed. © 2012 Pearson Education, Inc.

11 © 2012 Pearson Education, Inc.
Solutions Solutions are homogeneous mixtures of two or more pure substances. In a solution, the solute is dispersed uniformly throughout the solvent. © 2012 Pearson Education, Inc.

12 © 2012 Pearson Education, Inc.
Solutions The intermolecular forces between solute and solvent particles must be strong enough to compete with those between solute particles and those between solvent particles. © 2012 Pearson Education, Inc.

13 How Does a Solution Form?
As a solution forms, the solvent pulls solute particles apart and surrounds, or solvates, them. © 2012 Pearson Education, Inc.

14 How Does a Solution Form?
If an ionic salt is soluble in water, it is because the ion–dipole interactions are strong enough to overcome the lattice energy of the salt crystal. © 2012 Pearson Education, Inc.

15 © 2012 Pearson Education, Inc.
Student, Beware! Just because a substance disappears when it comes in contact with a solvent, it doesn’t mean the substance dissolved. It may have reacted. © 2012 Pearson Education, Inc.

16 © 2012 Pearson Education, Inc.
Student, Beware! Dissolution is a physical change—you can get back the original solute by evaporating the solvent. If you can’t get it back, the substance didn’t dissolve, it reacted. © 2012 Pearson Education, Inc.

17 Factors Affecting Solubility
Chemists use the axiom “like dissolves like.” Polar substances tend to dissolve in polar solvents. Nonpolar substances tend to dissolve in nonpolar solvents. © 2012 Pearson Education, Inc.

18 Factors Affecting Solubility
The more similar the intermolecular attractions, the more likely one substance is to be soluble in another. © 2012 Pearson Education, Inc.

19 Factors Affecting Solubility
Glucose (which has hydrogen bonding) is very soluble in water, while cyclohexane (which only has dispersion forces) is not. © 2012 Pearson Education, Inc.

20 © 2012 Pearson Education, Inc.
Temperature Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature. © 2012 Pearson Education, Inc.

21 © 2012 Pearson Education, Inc.
Temperature The opposite is true of gases. Carbonated soft drinks are more “bubbly” if stored in the refrigerator. Warm lakes have less O2 dissolved in them than cool lakes. © 2012 Pearson Education, Inc.

22 Factors Affecting Solubility
Vitamin A is soluble in nonpolar compounds (like fats). Vitamin C is soluble in water. © 2012 Pearson Education, Inc.

23 © 2012 Pearson Education, Inc.
Types of Solutions Saturated In a saturated solution, the solvent holds as much solute as is possible at that temperature. Dissolved solute is in dynamic equilibrium with solid solute particles. © 2012 Pearson Education, Inc.

24 © 2012 Pearson Education, Inc.
Types of Solutions Unsaturated If a solution is unsaturated, less solute than can dissolve in the solvent at that temperature is dissolved in the solvent. © 2012 Pearson Education, Inc.

25 © 2012 Pearson Education, Inc.
Types of Solutions Supersaturated In supersaturated solutions, the solvent holds more solute than is normally possible at that temperature. These solutions are unstable; crystallization can usually be stimulated by adding a “seed crystal” or scratching the side of the flask. © 2012 Pearson Education, Inc.

26 Immiscible - describes a process in which 2 liquids will not mix
Miscible – describes a process in which 2 liquids will mix (dissolve in each other) Water and alcohol Immiscible - describes a process in which 2 liquids will not mix Water and oil

27 Water in biological systems
Water has many unique properties because of it’s polarity and hydrogen bonding

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