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Acids and Bases

Chapter 15. Acids and Bases. ACIDS. Examples of acids: Vinegar Lemon Juice Soft Drink Battery Acid Stomach Acid Apple Juice Black Tea. ACIDS produce solutions that:. Taste sour. Turn blue litmus paper red. Conduct electricity. React with metals to liberate a hydrogen gas.

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Acids and Bases

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  1. Chapter 15 Acids and Bases

  2. ACIDS • Examples of acids: • Vinegar • Lemon Juice • Soft Drink • Battery Acid • Stomach Acid • Apple Juice • Black Tea

  3. ACIDS produce solutions that: • Taste sour • Turn blue litmus paper red • Conduct electricity • React with metals to liberate a hydrogen gas • Are corrosive (acid rain) • React with bases to form salt and water

  4. BASES • Examples of bases: • Detergent • Baking Soda • Drain Cleaner • Ammonia • Soaps (hand, dish) • Antacid

  5. Bases produce solutions that: • taste bitter • turn red litmus blue • conduct electricity • feel slippery • are corrosive (basic solution in glass container) • reacts with acids to form salt and water

  6. ACID-BASE THEORIES There are three common acid-base theories: • the Arrhenius theory • the Bronsted-Lowry theory • the Lewis theory

  7. SUMMARY OF ACID-BASE THEORIES THEORY ACID DEFINITION BASE DEFINITION Any substance which releases H+ ion in water solution. Any substance which releases OH- ions in water solution. Arrhenius Theory Any substance which donates a proton/hydrogen ion. Any substance which accepts a proton/hydrogen ion. Bronsted-Lowry Theory Lewis Theory Any substance which can accept an electron pair. Any substance which can donate an electron pair.

  8. Arrhenius Theory • Svante Arrhenius was a Swedish chemist. • In 1887, he published a paper concerning acids and bases. • He concluded that solutions with acids and bases in them released particles when dissolved. • He concluded that acids were substance which separated (ionized) in water solution to produce hydrogen ions (H+, or free protons). • He also believed that bases were substance which ionized to produce hydroxide ions (OH-) in water solution.

  9. Acid/Base reactions: Neutralization Produce water and a salt (and sometimes carbon dioxide). Hint: concentrate on the water first. Remember, water has the formula HOH. Complete and balance the following: HCl + KOH  HOH + KCl HCl + Ca(OH)2 2 2HOH + CaCl2 Require equal numbers

  10. 1. Ba(OH)2 + H3PO4 2. HC2H3O2 + NaOH 3. H2SO4 + KOH 4. H2CO3 + NaOH 5. Na2CO3 + HCl 

  11. BRONSTED-LOWRY THEORY • T. M. Lowry was an English scientist, while J. N. Bronsted was a Danish scientist. • In 1923, they independently proposed a new definition of the terms acid and base. • They stated that in a chemical reaction, any substance which donates a proton/hydrogen ion is an acid and any substance which accepts a proton/hydrogen ion is a base. Bronsted Lowry

  12. HF + H2O  F - + H3O+ Acid Base Conjugate Conjugate Base Acid Acids lose a hydrogen to become a conjugate base Bases gain a hydrogen to become a conjugate acid Conjugates:

  13. Example: Determine the acid, base, conjugate acid, and conjugate base in each of the following equations: HCl + H2O  Cl- + H3O+ Acid Base Conjugate Conjugate   Base Acid  H2SO4 + H2O  HSO4- + H3O+ Acid Base Conjugate Conjugate   Base Acid NH3 + H2O  OH- + NH4+ Base Acid Conjugate Base Conjugate Acid

  14. What is the conjugate base of the following substances? H2O ________________ NH4+________________ HNO2_______________ HC2H3O2_________________ 3. What is the conjugate acid of the following substances? HCO3-__________________ H2O____________ HPO42-____________ NH3___________

  15. LEWIS THEORY • Gilbert Newton Lewis was and American chemist. • In 1923, proposed an even broader definition of acids and bases. • Lewis focused on electron transfer instead of proton transfer. • He defined and acid as an electron-pair acceptor, and a base as an electron-pair donor. • This definition applies to solutions and reactions which do not even involve hydrogen or hydrogen ions. • His theory is used in organic chemistry.

  16. Strong and Weak Acids/Bases The strength of an acid (or base) is determined by the amount ofIONIZATION.

  17. Strong Acids/Bases:an acid that ionizes (separates into ions) completely or very nearly completely in aqueous solutions Weak Acids/Bases:an acid that ionizes only slightly in dilute aqueous solutions My uncle was a chemist, a chemist he's no more for what he thought was H 2 O was H 2 S O 4. (Ha Ha) Strong and Weak Acids/Bases

  18. Let’s examine the behavior of an acid, HA, in aqueous solution. HA What happens to the HA molecules in solution?

  19. 100% dissociation of HA HA H+ Strong Acid A- Would the solution be conductive?

  20. Partial dissociation of HA HA H+ Weak Acid A- Would the solution be conductive?

  21. HA  H+ + A- HA H+ Weak Acid A- At any one time, only a fraction of the molecules are dissociated.

  22. Strong Acids: 100% ionized (completely dissociated) in water. HCl + H2O  H3O+ + Cl- Strong Acids: Perchloric HClO4 Chloric, HClO3 Hydrobromic, HBr Hydrochloric, HCl Hydroiodic, HI Nitric, HNO3 Sulfuric, H2SO4

  23. What is a strong Base? A base that is completely dissociated in water (highly soluble). NaOH(s)  Na+ + OH- Strong Bases: Group 1A metal hydroxides (LiOH, NaOH, KOH, RbOH, CsOH) Heavy Group 2A metal hydroxides [Ca(OH)2, Sr(OH)2, and Ba(OH)2]

  24. Weak Acids: “The Rest”

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