Unit 16: Acids & Bases
Reading
BJU Chemistry: Ch. 16 "Acids, Bases, and Salts"
Zumdahl Chemistry: Ch. 14 "Acids and Bases"
Topics
Labs
BJU Chemistry: Ch. 16 "Acids, Bases, and Salts"
Zumdahl Chemistry: Ch. 14 "Acids and Bases"
Topics
- Properties of acids and bases
- Arrhenius model & Bronsted-Lowry model
- pH scale
- Neutralization
- Titration
Labs
- Acid-base titration lab
- "pH Scale" PhET weblab
- "Acid Base Solutions" PhET weblab
Below: Reacting aluminum metal with a strong acid (HCl or hydrochloric acid) and a strong base (NaOH or sodium hydroxide). Aluminum is a 'reactive' metal - which means it easily gives up its valence electrons.
| 16._acids_and_bases_class_notes1.docx |
Lecture outline
For an excellent (brief) overview of Acids & Bases, click here https://chem.libretexts.org/..../Overview_of_Acids_and_Bases
For an excellent (brief) overview of Acids & Bases, click here https://chem.libretexts.org/..../Overview_of_Acids_and_Bases
- Acids contribute hydrogen ions (H+) when they are in aqueous solution. You'll notice that acids begin with 'H', as in HCl (hydrochloric acid), H2SO4 (sulfuric acid), and HNO3 (nitric acid). Example: HCl dissociates in aqueous sol'n to form H+ and Cl- ions.
- The released hydrogen ion (it's just a proton, after all) doesn't hang around by itself. It immediately attaches to a nearby water molecule, giving rise to the 'hydronium ion' H3O+. That's why we always write it as H3O+, not H+. So more precisely, HCl plus H20 forms H30+ and Cl-.
- Bases contribute hydroxide ions (OH-) when they are in aqueous solution. You'll notice that most bases have 'OH' at the end, as in NaOH (sodium hydroxide or caustic soda), KOH (potassium hydroxide or potash), and Ca(OH)2 (calcium hydroxide or lime). Example: NaOH dissociates in aqueous sol'n to form Na+ and OH- ions.
- This description of acids & bases (above) was developed by Svante Arrhenius, probably the most respected chemist in the world around the 1880's.
- The Bronsted-Lowry model (1920's) expands the definitions of "acid & base" a little bit more. A Bronsted-Lowry acid donates a proton, while a base accepts a proton.
- The classic example of a Bronsted-Lowry base is ammonia (NH3). We know that NH3 acts as a base in solution (it will neutralize acids, for instance), but NH3 doesn't have an OH- ion... so how can it be a base? It can act as a base, according to the B-S definition, because it will accept a proton in solution. Consider: NH3 + HCl = NH4+ + Cl-. Here, NH3 acts as a base (it accepts a proton to become NH4+, and HCl acts as an acid (it contributes a proton to become Cl-).
- A strong acid plus a strong base yields a salt plus water. The classic example is: HCl + NaOH yields NaCl + H20.
- The pH scale goes from 0-14. Less than 7 is acidic, greater than 7 is basic, and equal to 7 is neutral.
- The pH scale is a logarithmic scale. You will need a calculator with a 'log' button. We will discuss...
- We will learn the equations for acid-base titrations, and for the pH scale.
Acid-Base Titration lab
This is the classic acid-base lab exercise. We will use glass burettes (handle them carefully!), mag stirrers, hydrochloric acid, and sodium hydroxide. The pH indicator will be phenolphthalien. I will hand out the lab instructions at the lab session. If you aren't able to complete the lab write-up at class, you can upload it to Canvas when finished.
This is the classic acid-base lab exercise. We will use glass burettes (handle them carefully!), mag stirrers, hydrochloric acid, and sodium hydroxide. The pH indicator will be phenolphthalien. I will hand out the lab instructions at the lab session. If you aren't able to complete the lab write-up at class, you can upload it to Canvas when finished.
| acid-base_titration_class_notes.docx |
pH Scale WebLab
| 16._ph_scale_weblab.docx |
Acids & Bases homework problems
See the instructions in Canvas. The assignment consists of selected end-of-chapter problems. You can upload your completed work to Canvas, or bring it to the next class.
See the instructions in Canvas. The assignment consists of selected end-of-chapter problems. You can upload your completed work to Canvas, or bring it to the next class.
| 16._acids___bases_end_of_chapter_questions_bju_3rd_edition.pdf |
Cellulose Acetate lab (optional)
In this lab, we turn cotton (or paper) into plastic. Cellulose acetate is a very interesting, historic polymer.
In this lab, we turn cotton (or paper) into plastic. Cellulose acetate is a very interesting, historic polymer.
- Cellulose Acetate (CA) was a big improvement over the earlier "nitrocellulose", because it wasn't flammable!
- C.A. was used in Kodak film, and all kinds of consumer products, including clothing!
- It is used today in many products, including reverse osmosis membranes for water purification, and clothing.
| cellulose_acetate_student_handout.pdf |