1 / 28

Acids, Bases, and Indicators

Acids, Bases, and Indicators. Chapter 6, Activity 7. Arrhenius Acids and Bases. Svante Arrhenius (1800s) Defined acids as those compounds that produced hydrogen ions (H + ) in water Examples: HCl – hydrochloric acid H 2 CO 3 – carbonic acid H 2 SO 4 – sulfuric acid.

ira
Download Presentation

Acids, Bases, and Indicators

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Acids, Bases, and Indicators Chapter 6, Activity 7

  2. Arrhenius Acids and Bases • Svante Arrhenius (1800s) • Defined acids as those compounds that produced hydrogen ions (H+) in water • Examples: • HCl – hydrochloric acid • H2CO3 – carbonic acid • H2SO4 – sulfuric acid

  3. Arrhenius Acids and Bases • Bases produce OH- ions in water • Examples: NaOH, Mg(OH)

  4. Concept Test 1 • Decide if the compound is an acid or base: (type the word acid or base, type all three answers, separated by commas): • FrOH • HF • H3PO4

  5. Characteristics • ACIDS • Some react with metal to form H2 gas • Zn + 2HCl -> H2 + ZnCl2 • Corrosive • Sour taste • Turns litmus paper red • Produce H+ in water • BASES • Feel slippery, soapy • Bitter taste • Corrosive • Produce OH- in water PH between 0 and 7 PH between 7 and 14

  6. Turn and Talk • Make a T-chart as below and fill in at least three of each, acid and base, that you might find in your home, school, or workplace. Be prepared to justify your answers:

  7. Example Acid Chemical Equation in water HCl(g) ------> H+(aq) + Cl-(aq) The H+ attaches itself to a water molecule: H+(aq) + H2O(l) -----> H3O+(aq) hydrogen water hydronium ion ion Combining the two gives the full equation: HCl(g) + H2O(l) -----> H3O+(aq) + Cl- (aq)

  8. Example Base Chemical Equation in water NaOH(s) ------> Na+(aq) + OH-(aq)

  9. There are other definitions of acids and bases • Not every acid produces H+ in water • Example: FeCl3 • Not every base produces OH- in water • Example: NH3 • Other definitions are needed • Brønsted-Lowry definition • Lewis definition • More on these later

  10. Neutralization Reactions HCl(aq) + NaOH(aq) -----> NaCl(aq) + H2O (l) • A special type of double-replacement reaction • Acid + base yields a salt plus water

  11. Concept Test 2 • Which of the following is a neutralization reaction? A) KCl + NaNO3 -> KNO3 + NaCl B) HNO3 + KOH -> H2O + KNO3 C) H2O + SO3 -> H2SO4 D) 4Na + O2 -> 2Na2O E) 2NO2 -> 2NO + O2

  12. Concept Test 3 • The neutralization reaction between Al(OH)3 and HNO3 produces the salt with the formula • H2O • AlNO3 • AlH2 • Al(NO3)3 • NO3OH

  13. Concentration • Recall: • Concentration is a measure of how much solute per unit of solvent there is. • Measured in units of molarity (M) • Example: 1.0 MHCl is more concentrated than 0.5 MHCl • REMEMBER! “Strong” does not mean concentrated in chemistry!

  14. What makes and acid or base “strong”? • Disassociates completely in water • Examples: • HCl • HBr • HI • HClO4 • Disassociates completely in water • Examples: • NaOH • KOH • Ca(OH)2 • Sr(OH)2 Strong acids Strong bases

  15. Concept Test 4 Ammonium hydroxide is a weak base because • A) it is a dilute solution. • B) it is only slightly soluble in water. • C) it cannot hold on to its hydroxide ions. • D) it dissociates only slightly in water. • E) it is completely ionized in aqueous solution.

  16. Concept Test 5 Which of the following is correctly identified? • A) NH3, strong acid • B) NaOH, strong base • C) HCl, weak acid • D) H2CO3, strong acid • E) Ca(OH)2, weak base

  17. Titration • You can calculate the concentration of an acid or base solution with a procedure called titration. • EXAMPLE: Find the concentration of an unknown acid solution: • Perform a neutralization reaction with a known concentration of base and an indicator. • When the endpoint is reached, the solution is neutral (the indicator changes color)

  18. What does titration look like?

  19. What does endpoint look like?

  20. Contrast: • Endpoint at pH = 7 • Example: HCl titrated with NaOH • Endpoint at pH higher than 7 • Example: • HC2H3O2 titrated with KOH Strong acid titrated with strong base Weak acid titrated with strong base

  21. Buffers • Solutions that resist changes in pH when a small amount of acid or base is added • Human blood is a natural buffer. Why? (Hint: Your blood should maintain a natural pH of 7.4)

  22. pH Scale

  23. pH Defined • pH = -log[H+] • Thus pOH = -log[OH-] • The brackets indicate concentration in chemistry. • This is a logarithmic scale; for each unit increase, the concentration increases tenfold.

  24. Practice calculation: • What is the pH of a 0.0115 M HCl solution?

  25. Concept Test 6 • What is the pH of a 0.089 M HBrsolution? • -0.05 • Undefined • -0.009 • 1.05 • 13.5 Note that HBr is a strong acid.

  26. Relationship between pH and pOH pH + pOH = 14

  27. Concept Test 7 • What is the pOH of a 0.0815 MNaOH solution? • (Numeric answer) • Note that NaOH is a strong base.

  28. Reminder: • Chem to Go is due tomorrow Chapter 6, Activity 7 Quiz on Friday If you will not be here, plan to take the quiz on Thursday

More Related