A1: Chapter 15.2 & 16.1 Aqueous Systems ( ) 1. Distinguish between a solution and an aqueous solution.

Transcription

1 A1: Chapter 15.2 & 16.1 Aqueous Systems ( ) 1. Distinguish between a solution and an aqueous solution. A solution is any substance dissolved into another substance. An aqueous solution is specifically a solute dissolved in water. 2. Define the following: Solute: The substance being dissolved that you put into the solution. Solvent: The substance that does the dissolving. The solvent is the foundation of the solution 3. Identify the solute and solvent in a dilute aqueous solution of potassium chloride. Potassium Chloride is the solute, water is the solvent. 4. Describe and diagram the process of solvation. 5. What is the significance of the statement likes dissolve likes? What does likes refer to? Polar substances will dissolve in Polar substances, non-polar will dissolve in non-polar. 6. Complete the following Electrolyte A compound that conducts an electrical current when dissolved In water or melted Nonelectrolyte Strong Electrolyte Weak Electrolyte A compound that does not conduct an electrical current when dissolved In water or melted A compound that completely dissociates in water. All of the compound become ions. A compound that only partially Ionizes when dissolved in water. Only a fraction of the compound exists as ions. NaCl, CuSO 4, NaOH, Strong acids, strong Bases. Sugar, alcohol Most salts, strong acids Strong bases Some salts, organic acids weak acids and bases.

2 7. Write equations to show how the following ionic compounds dissolve in water. Example: CaCl2(s) Ca 2+ (aq) + 2 Cl - (aq) a. KOH: KOH (s) K + (aq) + OH - (aq) b. Na3PO4: Na 3 PO 4(s) 3Na + (aq) + PO 4-3 (aq) 8. Which of the following compounds are soluble in water? Explain your answer in terms of polarity. a. CH 4 Not soluble because it is non-polar (perfect symmetry with tetrahedral shape) b. KCl Soluble because it is ionic and the ion charges like the polarity of water. c. He Not soluble because the atom is non-polar d. (NH 4 ) 2 CO 3 Soluble because it is ionic and the ion charges like the polarity of water. e. NH 3 Soluble because the molecule is polar (pyramidal shape with an unshared pair of electrons on the nitrogen) and likes the polarity of water. Solutions (pp ) 9. Name three factors that influence the rate at which a solute dissolves in a solvent. Temperature, surface area, disturbance(stirring), or pressure 10. Define saturated solution, solubility, and unsaturated solution. Saturated solution A solution in which the maximum amount of solute is dissolved in a given amount of solvent Solubility The maximum amount of solute that can dissolve in a given amount of solvent at a specific temperature. Unsaturated solution A solution in which less than the maximum amount of solute is dissolved in the solvent. The solution could dissolve more of the solute at that temperature. 11. Explain miscible and immiscible. Miscible is when a liquid can dissolve into another liquid. Immiscible is when liquids don t. 12. Describe two ways you could change: a. a saturated solution to an unsaturated solution 1. Add solvent 2. Heat the solution b. an unsaturated solution to a saturated solution 1. Remove solvent by evaporation or boiling 2. Cool the solution 3. Add solute. 13. Read page : If a saturated solution of sodium ethanoate is cooled, what change might you observe? The sodium ehanoate will begin to crystallize as the solution can t dissolve it all.

3 14. Use the solid substances listed in Table 16.1 on page 522 to make a general statement that relates a change in solubility of a solid to a change in temperature. Provide one example. Temperature rises, so does solubility. All of the lines curve up, meaning as temperature moves up to the right, the grams per volume also increase. 15. What mass of AgNO3 can be dissolved in 250 g of water at 20 C? How do you know? gagno 3 x gagno g H 2 O 250 g H 2 O, xgagno 3 ( (250g H 2O gagno 3 ) ) 555gAgNO 100 g H 2 O 3 A2: Chapter 16.2 Molarity Concentration of Solutions (pgs ) 1. A solution has a volume of 2.0 L and contains 36.0 g of glucose. If the molar mass of glucose is 180 g/mol, what is the molarity of the solution? volume (36 g C 6H 12 O L ) ( 1 molc 6H 12 O g C 6 H 12 O 6 ) M 2. A solution has a volume of 250mL and contains 0.70 mol NaCl. What is its molarity? ( n V ) volume (0. 7 mol 250 ml 3. Calculate the and grams of solute in each solution a. 1.0 L of 0.50 M NaCl volume, 50 mol NaCl (M)(V) (0. 1 L gnacl mol NaCl ( ) 29 gnacl 1 mol NaCl b. 5.0 x 10 2 ml of 2.0M KNO3 volume, ml ) (1000 ) 2. 8M 1 L ) (1. 0 L) mol NaCl 0mol (M)(V) (2. 1 L ) (5. 1L 00x102 ml) ( 1000mL ) 1. 0 mol KNO mol KNO 3 ( gkno 3 ) 101 gkno 1 mol KNO Find the molarity of a solution made from grams of chloric acid (HClO3) dissolved in 1700 ml of water. volume ( g HClO mL ) ( 1mol HClO 3 ) ( 1000mL ) M ghclo 3 1L 5. How many grams are needed to prepare 500 ml of a 2.5 M calcium fluoride solution? 5mol, (M)(V) (2. volume 1 L ) (500 ml) ( 1L 1000mL ) ( gcf 2 ) 98 gcaf 1 mol CaF 2 2

4 Percent Solutions %m/v %v/v 6. If 10mL of pure acetone is diluted with water to a total solution volume of 200mL, what is the percent by volume of acetone in the solution? % (v/v) V solute 10 ml. 05 5% (v/v) Volume Solution 200 ml 7. A bottle of hydrogen peroxide antiseptic is labeled 3.0% (v/v). How many ml H2O2 are in a ml solution? V solute % (v/v) Volume Solution, xml 3. 0mL (3. 0mL)(400mL), xml 12mL 400mL 100mL (100mL) 8. Calculate the grams of solute required to make 250 ml of 0.10% MgSO4 (m/v). % (m/v) Mass solute Volume Solution, xg 0. 10g 250mL 100mL, xml (0. 10g)(250mL) (100mL) 0. 25g 9. What is the concentration (in % (m/v) of 32 g NaNO3 in 2.0 L solution 2. 0L ( 1000mL ) 2000mL, % ( m ) Mass solute, 1L v Volume Solution 32g 2000mL % (m v ) 10. Hydrogen peroxide is often sold commercially as a 3.0% (m/v) aqueous solution. a. If you buy a 250 ml bottle of 3.0% H2O2, how many grams of hydrogen peroxide have you purchased? % ( m v ) Mass solute Volume Solution, xg 250mL 3. 0g 100mL, xml (3. 0g)(250mL) (100mL) 7. 5g b. What is the molarity of this solution? volume (3. 0gH 2O 2 100mL ) ( 1mol H 2O 2 ) ( 1000mL ) M g H 2 O 2 1L 11. How many grams ethyl alcohol are contained in 1 fluid ounce ( 30.0 ml) bourbon if the concentration of ethyl alcohol is 35.6% (m/v)? % (m/v) Mass solute Volume Solution x g , 30 ml xg 10. 7g 12. If I make a solution by adding water to 35 ml of methanol (CH3OH) until the final volume of the solution is 275 ml, what is the percent by volume of methanol in this solution(v/v%)? % (v/v) V solute 35 ml % v/v Volume Solution 275 ml

5 A3: Chapter 16.3 Making Dilutions (pgs ) 1. How many milliliters of a stock solution of 4.00M KI would you need to prepare ml of M KI? V 1 M 2 V 2 so, V 1 M 2V 2 (0. 760M)( ml) (4. 00M ) ml 2. Suppose you need 250mL of 0.20 M NaCl, but the only supply of sodium chloride you have is 1.0 M NaCl. How do you prepare the required solution? Assume that you have the appropriate volumemeasuring devices on hand. V 1 M 2 V 2 so, V 1 M 2V 2 (0. 20M)( ml) (1. 00M ) 50 ml 3. You have the following stock solution available; 4.0M KNO3, Calculate the volume you must dilute to make 50.0 ml of 0.20 M KNO3 V 1 M 2 V 2 so, V 1 M 2V 2 (0. 20M)(50. 0 ml) (4. 0M ) 2. 5 ml 4. How many ml of a 5.0 M stock solution are needed to prepare 200 ml of a 0.5 M solution? V 1 M 2 V 2 so, V 1 M 2V 2 (0. 5M)(200 ml) (5. 0M ) 20 ml 5. Describe how one would make 500 ml of a 5.5 M NaCl solution from a stock solution of 12M: V 1 M 2 V 2 so, V 1 M 2V 2 (5. 5M)(500 ml) (12M ) 230 ml 6. How many liters of stock 12 molar hydrochloric acid would you need to make 300 ml of 1.0 molar hydrochloric acid? After showing work, diagram and describe the process in words. V 1 M 2 V 2 so, V 1 M 2V 2 (10. M)(300 ml) (12M ) 25 ml I would pour 25 ml of 12 molar stock solution into a 300mL volumetric flask. Then I would dilute with water until it was exactly 300 ml. This would be a less concentrated solution of 1.0 molar.

6 A4: Ch 19.1 Acid Base Theories (pgs ) 1. Give the Bronsted-Lawry definition of an acid with an example. Hydrogen-ion donor (proton donor) i.e. HNO 3 2. Give the Bronsted-Lawry definition of a base with an example. Hydrogen-ion acceptor (proton acceptor) i.e. NH 3 3. Define a conjugate acid and a conjugate base. What is a conjugate pair? Give examples. Conjugate acid: Particle formed when a base gains a hydrogen ion, NH 3 NH 4 + Conjugate base: Particle formed when an acid donates (loses) a hydrogen ion, HCl Cl - 4. What does amphoteric mean? Provide an example. Amphoteric is a substance that can act as an acid or base. A good example is HSO Using the table (19.3) on page 651, tell whether you expect each substance listed to behave as an acid or a base, and give its conjugate partner. Acid or Base Conjugate Pair 1. HCl Acid Cl- 2. OH - Base H 2 O 3. H 2 SO 4 Acid HSO 4-4. NH + 4 Acid NH 3 5. Cl - Base HCl 6. Identify each of the following reactants as either an acid or a base. Also label the two products as conjugate acid-base pairs. 1. NH3 + H2O ---> OH - + NH4 + B A CB CA 2. HCl + H2O ---> H3O + + Cl - A B CA CB 3. CH3COOH + H2O <---> H3O + + CH3COO - A B CA CB 7. Predict, Apply & Synthesize: a. Write the equation for the ionization of hydrocyanic acid (HCN) with water. Label the acid, base, conjugate acid, and conjugate base. HCN + H 2 O H 3 O + + CN - A B CA CB b. Write the equation for the ionization of CO3 2- with water. Label the acid, base, conjugate acid, and conjugate base CO 3 + H 2 O HCO 3 + OH - B A CA CB

7 A5: Ch 19.2 Hydrogen Ions and Acidity (pgs ) 1. Draw the equation for water self ionization and explain what it means. H 2 O H + + OH -, In this ionization equation, water splits into hydrogen ions and hydroxide ions. 2. What happens when [H + ] increases? What happens when [H + ] decreases? When [H + ] increases [OH - ] decreases and the acidity increases. When [H + ] decreases [OH - ] increases and the acidity decreases. 3. What is the equation for the ion product for water? How does this relate to question #1? K w [H + ][OH - ] 1.00 x Explain what an acidic solution is using an example. An acidic solution is when the [H + ] is greater than 1.0 x 10-7 M and the [OH - ] is less than 1.0 x 10-7 M. 5. Explain what a basic solution is using an example. An basic solution is when the [H + ] is less than 1.0 x 10-7 M and the [OH - ] is greater than 1.0 x 10-7 M. 6. Classify each solution as acidic or basic, or neutral. a. [H + ] 6.0 x M Basic b. [OH - ] 3.0 x 10-2 M Basic b. [H + ] 2.0 x 10-7 M Acidic d. [OH - ] 1.0 x 10-7 M Neutral 7. If the hydroxide-ion concentration of an aqueous solution is 1 x 10-3 M, what is the [H + ] in the solution? Is the solution acidic, basic, or neutral? [H + ][OH - ] 1.00 x 10-14, so [H + ] 1.0x10-14 /1x10-3 1x10-11 M, Basic 8. What is ph, and what is the equation for calculating it? ph - log[h + ] 9. Find the ph of each solution a. [H + ] M ph - log[h + ] -log[0.045] 1.3 b. [H + ] 8.7 x 10-6 M 5.1 c. [H + ] M Calculate [H + ] for each solution. a. ph 5.00 [H + ] 10 -ph x10-5 M b. ph x10-13 M 11. Calculate the ph of each solution. a. [OH - ] 4.3 x 10-5 M ph 9.6 b. [OH - ] 5.0 x 10-9 M ph 5.7

8 12. You add a substance to pure water and the ph rises from 7 to 9. What has happened to the concentration of H3O + ions? The concentration of H 3 O + ions decreases as you go from a ph of 7 to 9 because the 7 represents [H 3 O + ] of 10-7 and the 9 represents is 100 times smaller than 10-7 Is the substance added an acid or a base? The substance added must have been a base because it received the H 3 O + ions, therefore causing a reduction in the concentration of the H 3 O + ions. Bases are H 3 O + ion receivers. 13. A friend claims that a 1.0 M HCl solution contains no OH - ions. Do you agree? Explain your answer. This cannot be true since [OH - ][H 3 O + ] Therefore, if OH - were zero, the answer could not equal What is the ph of a solution of M KOH solution? The [H + ] 1.0 x / x M. Therefore, the ph -Log [1.8 x ] Use the following equations to complete the table. ph - log [H3O + ] Kw [H3O + ][OH - ] 1.0 x [H + ] 10 -ph SUBSTANCE ph [H3O + ] [OH - ] Acid or Base apple juice x 10-4 M 3.16 x M Acid drain cleaner x x 10-1 M Base window cleaner x x 10-3 M Base strawberries x 10-4 M 3.1 x M Acid sea water x 10-8 M 7.4 x 10-7 M Base lemon juice x 10-3 M 2.0 x M Acid 16. Solution A has a ph of 3.0 and solution B has a ph of 5.0. Which solution has a larger concentration of H3O + ions? Solution A is more acidic and so it has more H 3 O + ions. How many times larger? 100x larger because 10-5 (100) 10-3 Which solution has the larger concentration of OH - ions? Solution B is less acidic and more basic so it has more OH - ions. How many times larger? 100 times more 17. Solution A has a ph of 8.0 and solution B has a ph of Which solution has a larger concentration of OH - ions? Solution B is more basic and so it has more OH - ions. How many times larger? 1000x larger because (1000) 10-8 Which solution has the larger concentration of H3O + ions? Solution A is more acidic and so it has more H 3 O + ions. How many times larger? 1000x larger 18. Determine the ph of a 2.50 x 10-6 M HNO3 solution. Since this acid completely dissociates, the ph log[2.5x10-6 ] Determine the ph of a M NaOH solution. The [H + ] 1.0 x / x M. Therefore, the ph -Log [2 x ] What is the [H3O + ] of a solution having a 4.6 x 10-5 M of OH - ions? [H 3 O + ] 1.0 x /4.6 x x M