Bell Ringer What is the volume of one mole of a gas at STP?
Bell Ringer Identify the pH associated with acids and bases.
Acids and Bases
Bell Ringer Give two ways that acids are different from bases that does not include their pH.
Properties of Acids • pH < 7.0 • Electrolytes • Taste Sour • React with bases to form H2O + Salt • React with metals to form H2(g) and salt Table J
Properties of Bases • pH > 7.0 • Electrolytes • Taste Bitter • React with acids to form H2O + Salt • Slippery, soapy feeling
What is an acid? Arrhenius gives off an H+ and forms H3O+ - increases the H+ when dissolved in water Bronsted proton [H+] donor (loses an H+) HCl H+ + H2O H+ + Cl- H3O+
What is a base? Arrhenius gives off an OH- NaOH + HCl H2O and NaCl Bronsted proton [H+] acceptor (gains an H+) NaOH Ca(OH)2 Na+ + OH- Ca+2 + OH- 2
Universal Indicator pH Indicators Chemicals which change colors when they are put into acids or bases. These indicators change colors in response the [H+]. Table M
Bell Ringer If you were to place H2SO4 onto a piece of copper, would it react to produce hydrogen gas? Explain your answer.
MA= molarity of acid VA= volume of acid MB= molarity of base VB= volume of base Neutralization reactions - Products are always water and salt • Perform titrations to determine an unknown volume or concentration of an acid/base • ENDPOINT = when indicator changes color • Moles of H+ = Moles of OH- MAVA = MBVB
MA= molarity of acid VA= volume of acid MB= molarity of base VB= volume of base Titration problems If 20.0ml of a 0.50M HCl solution is needed to neutralize 65.0ml of a NaOH solution. What was the concentration of the base? MAVA = MBVB (0.5M)(20.0ml) = MB(65.0ml) MB= 0.154M
MA= molarity of acid VA= volume of acid MB= molarity of base VB= volume of base Titration problems 43.0ml of HCl was titrated with 32.0 ml of 0.100 M NaOH. What is the molarity of the hydrochloric acid solution? MAVA = MBVB MA(43.0ml)=(0.100M)(32.0ml) MA= 0.0744 M
Go over homework pH Indicators
Conjugate Acid-Base Pairs Strong acids have weak conjugate bases Weak acids have strong conjugate bases HCl + KOH HOH + KCl acid base conj. acid conj. base H2CO3 + 2NaCl Na2CO3 + 2HCl base acid conj. acid conj. base HSO4- + H3O+ H2O + H2SO4 conj. acid acid base conj. base
Practice Problems Identify the acid, base, conjugate acid, conjugate base, and conjugate acid-base pairs: HC2H3O2(aq) + H2O(l) C2H3O2–(aq) + H3O+(aq) conjugate base conjugate acid acid base conjugate acid-base pairs OH–(aq) + HCO3–(aq) CO32–(aq) + H2O(l) acid conjugate base conjugate acid base conjugate acid-base pairs
Bell Ringer Information related to an experiment is listed below: H2SO4 + 2KOH K2SO4 + 2H2O Results Based on the above results, what is the concentration of H2SO4?
MA= molarity of acid VA= volume of acid MB= molarity of base VB= volume of base Titration problems Calculate the molarity of an acetic acid solution if 34.57 mL of this solution are needed to neutralize 2.519 cL of 0.1025 M sodium hydroxide MAVA = MBVB (MA)(34.57ml) = (0.1025M)(25.19ml) MA= 0.07469M
Bell Ringer What are electrolytes? Give two examples.
Homework Answers p.185 q46-57 • 46) 25 mL • 3000 mL • 20 mL • 50.0 mL • 6.0 M • 0.60 M • 400 mL • 1.0 M • SKIP Cl 55) H + 56) O H H H - 57) O H
What is pH? • a way to measure the concentration of H+ ions (H3O+) in a solution • concentration of H+ = [H+] pH = -log[H+] If [H+] = 1 x 10-4, then pH = 4 If [H+] = 1 x 10-13, then pH = 13 If [H3O+] = 1 x 10-7, then pH = 7
Practice pH As the pH of a solution is changed from 3 to 6, how does the concentration of hydronium ions change? What is the pH of a 0.00001 molar HCl solution? If the pH of your pool is 6, what is the concentration of hydronium ions in solution? An aqueous solution that a [H+] of 1.0 x 10-8 mole per liter has a pH of?
pH What is the difference in [H+] in a pool that has a pH of 6, but in reality you want it to have a pH of 7? • Because it is a logarithmic scale, each one unit change in pH really represents a 10 fold change in [H+] • So going from a pH of 6 to 7 really represents a 10 fold decrease in the number of [H+]
pH and pOH [H+][OH-] = 10-14 pH + pOH = 14 If [OH] = 10-8 M, what is the pH? Solution: • the OH = 8, so the pH must be 14 – 8 • So the pH = 6
Bell Ringer Solution A has a pH of 1 and solution Z has a pH of 5. How many times greater is the hydronium ion concentration in solution A?
Buffers • A compound that does not allow the pH to change even if an acid or base is added to the system • They have the ability to absorb/release H+ which will keep the pH relatively constant • Good buffers are amphiprotic substances • Amphiprotic – something that can act as an acid and a base
Brooktrout Lake Buffers • Blood pH • Adirondack lakes "Treat the earth well: it was not given to you by your parents, it was loaned to you by your children. We do not inherit the Earth from our Ancestors, we borrow it from our Children."
Effects of Acid Rain on Marble(marble is calcium carbonate) George Washington: BEFORE acid rain George Washington: AFTER acid rain
Bell Ringer The pH of a lake is 8.0. Over a 10 year period, the pH of the water becomes 1000x more acidic. • Name an ion that has increased in the water over the 10 years? • What is the pH now? • If you were to use bromothymol blue to test the pH, what color would it be? [Use R.T.]
Bronsted-Lowry Acids and Bases wkst 1. H2O + H2O H3O+ + OH- 2. H2SO4 + OH- HSO4- + H2O 3. HSO4- + H2O SO4-2 + H3O+ 4. OH- + H3O+ H2O + H2O 5. NH3 + H2O NH4+ + OH-
Conjugate Acid-Base Pairs wkst H2PO4- H3PO4 ↔ H+ + H2PO4- HF HF ↔ H+ + F- HNO3 HNO3 ↔ H+ + NO3- HPO4-2 H2PO4- ↔ H+ + HPO4-2 OH- H2O ↔ H+ + OH- HSO4- HSO4-↔ H+ + SO4-2 PO4-3 HPO4-2 ↔ H+ + PO4-3 NH3 NH4+4 ↔ H+ + NH3 H3O+ H3O+ ↔ H+ + H2O
Topic 10 Regents Questions PART C 36. Reduces error, increases reliability 37. Ca(OH)2 + H2SO4 CaSO4 + 2H2O 38. pH= 6.0 39. 0.33 M 40. HCl – 9.50 ml NaOH – 3.80 ml 41. 0.25 mL 42. Methyl orange, brom blue, thymol blue 43. Between 4.4 and 5.5 44. Yellow • A, C, D • D • Presence of H+ ions • C • C • (10.01mL)(0.100M)= MB(5.01ml) • 0.200 M • 32. 7 • 33. Colorless to pink. • 34. 0.21 M • 35. 0.97 M
Topic 10 Regents Questions • 4 • 3 • 4 • 3 • 1 • 1 • 1 • 4 • 2 • 1 • 3 • 1 • 2 • 4 PART A PART B • 1 • 3 • 2 • 4 • 2 • 3 • 1 • 2 • 1 • 4 • 2
Bell Ringer In a lab there were three flasks, one filled with methanol, another had NaOH, and the third HCl. ID these liquids. • A student concluded that bottle C contained HCl. Identify one way that supports this finding. • Explain in terms of pH, why methyl orange was the same for all three liquids.
Bell Ringer What is the volume of 1.00 mole of any gas at STP? Hint: Lab