Introduction to Solutions

1. Introduction to Solutions

2. MIXTURE PURE SUBSTANCE yes no yes no Is the composition uniform? Can it be chemically decomposed? Colloids Suspensions Matter Flowchart MATTER yes no Can it be physically separated? Homogeneous Mixture (solution) Heterogeneous Mixture Compound Element

3. Pure Substances • A pure substance has a definite composition. • Pure substances can be elements or compounds

4. Mixtures • A mixture can be either homogeneous or heterogeneous. • A homogeneous mixture is one in which all of the components are UNIFORMILY distributed. • Ex: chocolate milk • A heterogeneous mixture is one in which the components are NOT UNIFORMILY distributed. • Ex: pizza HOMOGENEOUS HETEROGENEOUS

5. Solutions Solutions, in chemistry, are homogeneous mixtures of two or more substances. The substance present in largest quantity usually is called the solvent. The solvent can be either a liquid or a solid. The substance that is present in smallest quantity is said to be dissolved and is called the solute. The solute can be either a gas, a liquid, or a solid.

6. Concept Check Coke lists as its ingredients as: “carbonated water, high fructose corn syrup and/or sucrose, caramel color, phosphoric acid, natural flavors, caffeine”. What is the solvent? What are the solutes? What can we classify CO2 as in carbonated beverages?

7. Miscible liquids can easily dissolve in one another. • Immiscible liquids are not soluble in each other. IPC-Solutions-Borders

8. Heterogeneous Mixtures • Suspensions-a heterogeneous mixture that contains large particles that “settle out” unless constantly stirred or agitated • Ex: freshly squeezed OJ, salad dressing • Colloids-a heterogeneous mixture in which the components are microscopic and will not separate when left standing. • Ex: mayonnaise, milk, stick deodorant

9. How does a solid dissolve into a liquid? • Solvent molecules are attracted to surface ions. • Each ion is surrounded by solvent molecules. Ionic solid dissolving in water

10. dry Dissolution vs. Reaction • Dissolution is a physical change—you can get back the original solute by evaporating the solvent. • If you cant, the substance didn’t dissolve, it reacted. Ni(s) + HCl(aq) NiCl2(aq) + H2(g) NiCl2(s)

11. Factors Affecting Solubility • Chemists use the saying “like dissolves like:” • Polar substances tend to dissolve in polar solvents. • Nonpolar substances tend to dissolve in nonpolar solvents. Oil is nonpolar while water is polar. They are immiscible.

12. Saturation Types • Saturated • Unsaturated

13. Degree of saturation • Unsaturated Solution • Less than the maximum amount of solute for that temperature is dissolved in the solvent. • No solid remains in flask.

14. Degree of saturation • Saturated solution • Solvent holds as much solute as is possible at that temperature. • Undissolved solid remains in flask. • Dissolved solute is in dynamic equilibrium with solid solute particles.

15. Saturated Solution IPC-Solutions-Borders

16. Degree of saturation • Supersaturated Solution • Solvent holds more solute than is normally possible at that temperature. • These solutions are unstable

17. Temperature and Solubility Generally, the solubility of solid solutes in liquid solvents increases with increasing temperature.

18. Solubility What amount of CaCl2 can be dissolved in 100 g H2O at 20° C? ANSWER: 75 g CaCl2

19. Let’s play a quick game of…. Saturated or Unsaturated? IPC-Solutions-Borders

20. Saturated or Unsaturated? • a solution that contains 70g of NaNO3 at 30°C IPC-Solutions-Borders

21. Unsaturated! IPC-Solutions-Borders

22. Saturated or Unsaturated? • a solution that contains 50g of NH4Cl at 50°C IPC-Solutions-Borders

23. saturated! IPC-Solutions-Borders

24. Saturated or Unsaturated? • a solution that contains 20g of KClO3 at 50°C IPC-Solutions-Borders

25. saturated! IPC-Solutions-Borders

26. Saturated or Unsaturated? • a solution that contains 70g of KI at 0°C IPC-Solutions-Borders

27. Unsaturated! IPC-Solutions-Borders

28. Saturated or Unsaturated? • A mass of 100 g of NaNO3 is dissolved in 100 g of water at 80ºC IPC-Solutions-Borders

29. Unsaturated! IPC-Solutions-Borders

30. THE END IPC-Solutions-Borders

31. Solubility of Gases • In general, the solubility of gases in water increases with increasing mass. Why? • Larger molecules have stronger dispersion forces. IPC-Solutions-Borders

32. Gases in Solution • The solubility of liquids and solids does not change appreciably with pressure. • But, the solubility of a gas in a liquid is directly proportional to its pressure. Increasing pressure above solution forces more gas to dissolve. IPC-Solutions-Borders

33. Temperature • The opposite is true of gases. Higher temperature drives gases out of solution. • Carbonated soft drinks are more “bubbly” if stored in the refrigerator. • Warm lakes have less O2 dissolved in them than cool lakes. IPC-Solutions-Borders

34. solubility increases with increasing temperature solubility decreases with increasing temperature Temperature and Solubility Solid solubility and temperature IPC-Solutions-Borders

35. Temperature and Solubility Gas solubility and temperature solubility usually decreases with increasing temperature IPC-Solutions-Borders

36. Electrolytes IPC-Solutions-Borders

37. Electrolyte Electrolyte: a substance that dissolves in water to give a solution that conducts electric current • Any soluble ionic compound is an electrolyte • Strong acids are electrolytes IPC-Solutions-Borders