Topic 9: Acids & Bases

Transcription

1 Topic 9: Acids & Bases Regents Chemistry Mr. Mancuso Electrolytes Substances that conduct electricity when Include Ability to conduct electricity is due to the presence of Dissociation: ~ 1 ~

2 Acids and Bases Operational Definition: Conceptual Definition Operational Definitions (a) Acids (1) (2) ~ 2 ~

3 (3) (4) (5) ~ 3 ~

4 (b) Bases (1) (2) (3) (4) ~ 4 ~

5 Conceptual Definition of Acids and Bases (Arrhenius Theory) A higher concentration of H + A higher concentration of OH Water: H + is o o Acids Bases o HCl + H 2 O H 3 O + Organic acids NH 3 + H 2 O ~ 5 ~

6 Identifying Acids and Bases from their Definitions From each description, identify if the substance would be an acid or a base, or if there is not enough information to make a determination Substance #1: Turns litmus paper blue Has a ph of 10 Substance #2: Leaves a scum on surfaces Turns phenolphthalein pink Substance #3: Will not produce gas when poured on metal Substance #4: It s aqueous solution is a strong electrolyte When mixed with substance #3, it will produce salt and water Substance #5: It s aqueous solution contains a high number of hydronium ions Substance #6: Turns litmus paper purplish blue Accepts H + ions Substance #7: Will bubble when mixed with zinc metal When tested with phenolphthalein, the phenolphthalein remained colorless Substance #8: Your lab partner screams with terror when it is spilled on him. Mr. Mancuso rushes over and pours calcium hydroxide on the spill ~ 6 ~

7 ~ 7 ~

8 ph: (H + concentration) ph measures: poh measures: Both are based on the powers of 10 Molarity is a unit of concentration defined as number of moles of a substance per liter of solution. ~ 8 ~

9 ph poh Concentration of H + (M) x s weaker than ph 1 Relative concentrations ~ 9 ~

10 Salts Ionic compounds that Are strong Electronegativity differences of ; react Salts are produced in Hydrolysis: ~ 10 ~

11 Neutralization and Hydrolysis Complete the reactions for the following neutralizations. Name all compounds. 1. NaOH + HCl 2. KOH + HNO 3 3. KOH + H 2 CO 3 4. NH 4 OH + HCl 5. Ca(OH) 2 + HBr 6. NH 4 OH + H 3 PO 4 Complete the hydrolysis of the following compounds. Name all compounds 7. KCl + 8. K 2 SO KNO LiClO NaCl + ~ 11 ~

12 Acid Base Reactions Directions: Predict the products and completely balance the following reactions. (1) Demonstrate the hydrolysis of calcium carbonate. Name the acid produced. (2) Demonstrate the hydrolysis of sodium sulfite. Name the acid produced. (3) Show the neutralization of nitric acid with lithium hydroxide. Name the salt produced. (4) Show the neutralization of acetic acid with magnesium hydroxide. Name the salt produced. (5) Demonstrate the hydrolysis of ammonium chloride. Name the acid produced. ~ 12 ~

13 (6) What acid must sodium hydroxide react with to produce sodium chlorate? Show the reaction and identify if it is neutralization or hydrolysis. (7) What salt will produce beryllium hydroxide and phosphoric acid when mixed with water? (8) Predict the salt produced from the reaction of hypochlorous acid with calcium fluoride. Show the reaction. ~ 13 ~

14 Acid Base Titration A lab techniques used to determine the unknown molarity (concentration) of an acid or base ph indicators are used. Endpoint is where there is a color change M A V A (# H + ions) = M B V B (# OH ions) Other Indicators are identified on Table M Indicator ph of color Δ Color change Methyl orange Red to yellow Bromothymol blue Yellow to blue Phenolphthalein Colorless to pink Litmus Red to blue Bromcresol green Yellow to blue Thymol blue Yellow to blue ~ 14 ~

15 Table M: Common Acid Base Indicators & ph 1. What is the color of phenolphthalein in a solution whose ph is 11? 2. Thymol blue would be yellow in what ph range? 3. What indicator would be best for an acid base titration whose equivalency point is at a ph of 6.5? (1) methyl orange (2) bromthymol blue (3) phenolphthalein (4) thymol blue 4. A student tested an unknown solution. When tested with litmus paper, the litmus paper turned purple. When the solution was tested with methyl orange, the solution turned yellow. What is the ph range of the solution? 5. A student tested an unknown colorless solution. When the student tested the solution with phenolphthalein, the solution remained colorless. When tested with thymol blue, the solution turned yellow. When tested with bromthymol blue, the solution turned blue. What is the ph range of the unknown solution? 6. A student tested an unknown colorless solution. When the solution was tested with methyl orange, the solution turned orange. When tested with bromcresol green, it turned yellow. What is the ph range of this solution? 7. A student tested an unknown colorless solution. When the solution was tested with phenolphthalein, the solution turned pink. When the solution was tested with thymol blue, the solution turned green. What is the ph range of the solution? ~ 15 ~

16 Titration and Concentration (Molarity) Solve each question below. Use significant figures, and show all work. Also, write the balanced reaction for each. Guided Practice: (1) A volume of 30. ml of 0.25 M HCl neutralizes a 50. ml sample of KOH solution. What is the concentration of KOH? (2) A volume of 37 ml of 0.36 M KCN neutralizes a 75 ml sample of HClO solution. What is the concentration of HClO? (3) How many milliliters of 0.2 M NaOH are needed to neutralize 20 ml of 0.1 M HCl? (4) A volume of 50. ml of 0.30 M HCl neutralizes a 60. ml sample of Ca(OH) 2 solution. What is the concentration of Ca(OH) 2 ~ 16 ~

17 Student Practice: (5) A volume of 90 ml of 0.2 M HBr neutralizes a 60 ml sample of NaOH solution. What is the concentration of the NaOH solution? (6) A volume of 46 ml of 0.40 M NaOH neutralizes an 80. ml sample of HCN solution. What is the concentration of HCN? (7) A volume of 20. ml of 0.25 M Al(OH) 3 neutralizes a 75 ml sample of H 2 SO 4 solution. What is the concentration of H 2 SO 4? (8) A volume of 135 ml of 0.40 M HCl neutralizes a 90. ml sample of Ca(OH) 2 solution. What is the concentration of Ca(OH) 2? ~ 17 ~

18 (9) A volume of 60. ml of 0.60 M HBr neutralizes an 80. ml sample of Ca(OH) 2 solution. What is the concentration of Ca(OH) 2? (10) A volume of 10. ml of 0.75 M NaOH neutralizes a 30. ml sample of HClO solution. What is the concentration of HClO? (11) How many milliliters of 0.20 M HCl is needed to exactly neutralize 40. milliliters of 0.4 M KOH? (12) If 20. milliliters of 1.0 M HCl was used to completely neutralize 40. milliliters of an NaOH solution, what was the molarity of the NaOH solution? (13) If 20. milliliters of 4.0 M NaOH is exactly neutralized by 20. milliliters of H 2 CO 3, the molarity of H 2 CO 3 is: ~ 18 ~

19 (14) How many milliliters of 4.00 M NaOH are required to exactly neutralize 50.0 ml of a 2.00 M solution of HNO 3? (15) A 3.0 milliliter sample of HNO 3 solution is exactly neutralized by 6.0 milliliters of 0.50 M KOH. What is the molarity of the HNO 3 sample? ~ 19 ~

20 Unit Practice 1. According to the Arrhenius theory, when an acidic substance is dissolved in water it will produce a solution containing only one kind of positive ion. To which ion does the theory refer? (1) acetate (3) chloride (2) hydrogen (4) sodium 2. According to the Arrhenius theory of acids, citric acid in oranges and acetic acid in vinegar are classified as acids because their aqueous solutions contain: (1) hydrogen ions (3) hydroxide ions (2) hydrogen atoms (4) hydroxide atoms 3. Which compound is an electrolyte? (1) C 6 H 12 O 6 (3) CH 3 CH 2 OH (2) C 12 H 22 O 11 (4) CH 3 COOH 4. If 1 mol of each of the following substances were dissolved in 1 L of water, which solution would contain the highest concentration of H 3 O + ions? (1) CH 3 COOH (3) NaCl (2) KBr (4) Ba(OH) 2 5. Which species is classified as an Arrhenius base? (1) CH 3 OH 3 (3) PO 4 (2) LiOH 2 (4) CO 3 6. According to your reference tables, which metal would react spontaneously with hydrochloric acid? (1) gold (2) silver (3) copper (4) zinc 7. Which metal will release H 2 (g), when it reacts with HCl? (1) Au (s) (2) Zn (s) (3) Hg (l) (4) Ag (s) 8. Which type of reaction occurs when equal volumes of 0.1 M HCl and 0.1 M NaOH are mixed? (1) neutralization (3) electrolysis (2) ionization (4) hydrolysis ~ 20 ~

21 9. Which compound reacts with an acid to produce water and salt? (1) CH 3 Cl (3) CH 3 COOH (2) KCl (4) KOH 10. A water solution contains 0.50 mol of HCl. How much NaOH should be added to the HCl solution to exactly neutralize it? (1) 1.0 mol (3) 0.25 mol (2) 2.0 mol (4) 0.50 mol 11. Which substance is always produced by a neutralization reaction? (1) water (3) ester (2) acid (4) base 12. Which compound is a salt? (1) Na 3 PO 4 (3) CH 3 COOH (2) H 3 PO 4 (4) Ca(OH) Which formula represents a salt? (1) KOH (3) CH 3 OH (2) KCl (4) CH 3 COOH 14. When NaOH (aq) reacts completely with HCl (aq) and the resulting solution is evaporated to dryness, the solid remaining is: (1) an ester (3) a salt (2) an alcohol (4) a metal 15. Write the balanced equation for each of the following neutralization reactions and write the name of the salt formed: (a) phosphoric acid and lithium hydroxide (b) phosphoric acid and calcium hydroxide ~ 21 ~

22 16. To neutralize 1 mol of sulfuric acid, 2 mol of sodium hydroxide are required. How many liters of 1 M NaOH are needed to exactly neutralize 1 L of 1 M H 2 SO 4? (1) 1 (2) 2 (3) 0.5 (4) During an acid base neutralization, how many moles of hydroxide ions will react with one mole of hydrogen ions? (1) 1.0 mol (2) 0.5 mol (3) 17.0 mol (4) 22.4 mol 18. One liter of 1 M NaOH will completely neutralize one liter of: (1) 1 M H 2 SO 4 (3) 2 M H 2 SO 4 (2) 0.5 M H 2 SO 4 (4) 1.5 M H 2 SO A 2.0 L sample of NaOH solution is exactly neutralized by 4.0 ml of 3.0 M HCl solution. What is the concentration of the NaOH solution? 20. How many ml of 0.20 M hydrochloric acid is required to neutralize 100. ml of 0.80 M potassium hydroxide? 21. Write the electron dot diagram of a hydrogen chloride molecule. ~ 22 ~

23 22. Which ph value represents a solution with the lowest OH ion concentration? (1) 1 (2) 7 (3) 10 (4) As an acidic solution is added to a basic solution, the ph of the basic solution: (1) decreases (2) increases (3) remains the same 24. A solution was yellow in bromthymol blue and blue in bromcresol green. According to Table M in your reference tables, what could the ph of this solution be? 25. A solution was tested with a ph meter and found to have a ph of 7.8. What color would the solution have if the following indicators were added? (a) bromthymol blue (b) thymol blue ~ 23 ~