1. Solution chemistry

2. Objective 4: TEKS 9a, b, d: The student is expected to --- Relate the structure of water to its function, Relate the concentration of ions in a solution to physical and chemical properties such as pH, electrolytic behavior, and reactivity; and Demonstrate how various factors influence solubility including temperature, pressure, and nature of the solute and solvent.

3. Solutions Most of chemistry is based on solution chemistry, where water is the solvent. (These are called aqueous solutions). Solutions—homogeneous mixture of two or more substances completely dispersed(same throughout).

4. Common Solutions Examples: Salt water (salt dissolved in water) Vinegar (acetic acid dissolved in water) Milk of magnesia (magnesium hydroxide dissolved in water) Carbonated drinks (carbon dioxide gas dissolved in water)

5. The component that does the dissolving and is present in greater proportion is called the solvent. The component that gets dissolved is called the solute. A solution has two parts: Solute and solvent

6. Ocean water is a solution. What is the solute in ocean water? Sweet tea is also a solution. What is the solute in sweet tea?

7. What is solubility? The amount of a substance that dissolves in a given volume of solvent at a given temperature. Common units: grams solute/ 100 grams of solvent or grams solute/ 100mL of water

8. Factors Affecting Solubility #1: Solute-solvent interaction #1: Solute-solvent interaction Like dissolves like Polar liquids tend to dissolve in polar solvents. “Likes dissolve likes”. Example: Water and Ethanol are both polar, and are miscible. Polar water and non-polar oil are immiscible. Miscible liquids: mix in any proportions. Immiscible liquids: do not mix.

9. #2: Temperature Factor - Solids/Liquids- Solubility increases with Temperature. Increased K.E. increases motion and collisions between solute / solvent. Gas - Solubility decreases with Temperature. Increased K.E. results in gas escaping to atmosphere.

10. Why does sugar dissolve better in hot coffee than in cold coffee? The hot coffee has more kinetic energy, which causes the solute (sugar) and the solvent (coffee) to move faster, collide more often, and mix easier.

11. #3 Pressure Factor - Solids/Liquids - Very little effect. Solids and Liquids are already close together; extra pressure will not increase solubility. Gases in Liquids - Solubility increases with Pressure. Increased pressure squeezes gas solute into solvent.

12. Does more or less CO 2 gas dissolve in a soft drink when the lid is removed? Explain your answer. When the lid is removed, the pressure inside the bottle is greatly reduced. Fewer CO 2 molecules are forced into the liquid at the lower pressure, so less CO 2 dissolved. [Or we might say that the solubility of CO 2 is less in the open bottle.]

13. Properties of Water 2-2-  + Water is polar Water forms hydrogen bonds Ice is less dense than water

14. THE DISSOLVING PROCESS When an ionic solid dissolves in water, the ions that form the solid are released into solution, where they become associated with the polar solvent molecules. NaCl(s)  Na + (aq) + Cl - (aq) We can generally assume that salts dissociate into their ions when they dissolve in water.

15. +- The positive end of the water molecule is attracted to the anion (negative ion) and the negative end of the water molecule is attracted to the cation (positive ion). Solutions of ionic compounds are strong electrolytes.

16. Electrolytes: solutions that conduct an electric current. Electrolytes contain dissolved ions. Strong Weak Non Electrolyte Electrolyte Electrolyte solution

17. O O Covalent acids form ions in solution. Some covalent compounds IONIZE in solution H H H H H Cl H +- + + If the molecule ionizes completely it is a strong electrolyte, if it partially ionizes it is a weak electrolyte. HCl, hydrochloric acid, is a strong electrolyte and HC 2 H 3 O 2 (vinegar) or acetic acid, is a weak electrolyte.

18. Sugar is a molecular solid. When sugar dissolves in water, the weak bonds between the individual sucrose molecules are broken, and these C 12 H 22 O 11 molecules are released into solution. Sugar does not form ions in solution. No, because it does not contain ions and cannot conduct an electric current. Is sugar water an electrolyte?

19. Saturated Solutions

20. 1. Which substance’s solubility increases the most with temperature? Solubility Graph The solubility of KNO 3 increases at a greater rate with added temperature than the other substances

21. 2. What is the solubility of KI at 10 o C? The solubility of KI at 10 o C. is about 130 grams per 100 grams of water.

22. 4. How many grams of sodium phosphate, Na 3 PO 4, will dissolve in 200 g of water at 80 o C.? According to the graph, about 70 g of Na 3 PO 4 will dissolve in 100 g of water at 80 o C. So about 140 g will dissolve in 200 g of water.

23. Aqueous Solutions An aqueous solution is simply a water-based solution. They have special properties. Aqueous solutions of ionic compounds, acids, and bases all conduct electricity. A conductivity tester is used to see if aqueous solutions conduct electricity

24. Water Water naturally dissociates partly into hydrogen ions (H + ) and hydroxide ions (OH - ). H 2 O  H + + OH - Distilled water has a pH of 7, halfway up the scale, indicating a balance between H + and OH - ions in solution. 0 --------7--------14 strong acid ----neutral-------strong base Every aqueous solution has a little bit of hydrogen ions and a little bit of hydroxide ions. This means that every aqueous solution has a pH.

25. pH—A quick lesson The pH of a solution determines the acidity or alkalinity (“basic-ness”) of that solution. pH is actually a measure of the hydrogen ion concentration in solution. Acids are hydrogen ion donors…they give away H + ions to other compounds. Bases are hydrogen ion recipients…they accept H + ions from other compounds.

26. pH The pH scale is logarithmic, meaning that each whole number decrease indicates a tenfold (that 10 times!) increase in ion concentration. A neutral solution has a pH of 7. This means that the [H + ] = [OH - ].

27. Concentration vs. pH A “strong acid” or “strong base” is usually highly reactive and will either dump H + ions onto or rip H + ions from anything reactive in its environment. It is possible to dilute strong acids and bases so that while they are still “strong,” they can be safely handled, even spilled on the skin with little ill effect. The term “weak acid” describes a compound’s ability to give up a H + ion. A concentrated “weak acid” or “weak base” can take your skin off just as surely as any strong acid.

28. Acids (Properties) Taste Sour Turn Red litmus Blue Neutralizes bases Reacts with metals pH below 7 Examples: Juices: Tomato, Orange, Grapefruit Wine Banana Coffee Vitamin C Soda Acids-Bases Characteristics Base (Properties) Taste Bitter Turn Blue litmus Red Neutralizes acids Turns metal into hydroxides pH above 7 Slippery Examples: Milk of Magnesia Lime water Lye, Drano Ammonia blood Soap

29. Safety Strong acids are highly corrosive and strong bases are highly caustic. A strong, concentrated base is as harmful as any acid [probably better since many bases will cling to materials rather than rinse off easily with water (think soap…most detergents are bases.] Acids and bases should generally be handled with gloves to prevent chemical burns. Concentrated acids and bases should only be used in a fume hood or a well-ventilated area as the fumes can be just as reactive and dangerous as the liquid chemicals.

30. Problems: Two clear solutions are placed in separate beakers. The first solution has a pH of 4, and the pH of the second solution is unknown. If the two solutions are mixed and the resulting pH is 5, the second solution must have— A)Fewer suspended solids B)A lower temperature C)More dissolved salt (NaCl) particles D)A higher concentration of OH - ions TAKS 11 th grade science spring 2003 #33

31. ANSWER = D: A higher concentration of OH - ions The pH of the first solution was 4, but after the second solution was added, the pH raised to 5. So the solution became less acidic—or more basic. This means more OH - ions were added, since OH - ions cause solutions to be more basic.

32. Bathwater normally has electrolytic behaviors even though distilled water does not. This is because bathwater— A)Contains isotopes of hydrogen B)Has been heated C)Is separated into H + and OH - ions D)Contains dissolved minerals TAKS Spring 2004 11 th grade science # 24

33. A)Contains isotopes of hydrogen Isotopes have nothing to do with electrolytic behavior. B)Has been heated Heating water does not break it into ions. C) Is separated into H + and OH - ions Only a very tiny fraction of these ions are produced in water—not enough to case electrolytic behavior. ***D) Contains dissolved minerals Tap water contains many kinds of dissolved salts which dissolve into ions and cause the water to conduct an electric current.

34. The pH scale measures— A)The strength of an acid B)The strength of hydrogen ions C)The concentration of hydrogen ions D)The concentration of an acid TAKS Science Review Guide Spring 2002, State of Texas, pub. D is correct: By definition, pH measures the concentration of hydrogen ions.

35. At the same concentrations, strong acids produce more ________________ than weak acids. A)Hydroxide ions B)Hydrogen ions C)Oxygen ions D)Chloride ions TAKS Science Review Guide Spring 2002, State of Texas, pub.

36. ***B is the correct answer. Strong acids produce more hydrogen ions than weak acids. Strong acids total ionize (or break apart). Weak acids only partially ionize.