1. Chemistry 163- Intro Lab Monique Wilhelm

2. NEVER MISS LAB!!!!! One hour lecture Remaining time in lab 1credit class = at least 3 hours spent outside of class on class preparation Classroom Environment Lecture-open discussion style I EXPECT you to talk, too Help answer questions, etc. Do not be turned off if I answer a question with another question; my job is to show you how to problem-solve

3. What will we learn? Methods and equipment used in chem labs How to make decisions about experimentation What types of things are important to be aware of during experimentation How to draw conclusions about data obtained How to communicate your findings

4. Safety Overview Remember: Everything in Chemistry Lab has the potential to be harmful Goggles Gloves Absolutely No Eating or Drinking in Any Lab 5 Senses Attire Long Hair Tied Back Always wear long pants Never wear loose fitting long sleeved shirts NO sandals, closed shoes

5. Safety Continued Remember: Everything in Chemistry Lab has the potential to be harmful Labels Contact Excess Chemicals Material Safety Data Sheets (MSDSs) Explain the hazards associated w/ substances ALL chemicals have the POTENTIAL to be harmful

6. Your Grade Expectations Follow Directions Be Prepared Only one late assignment allowed NO make ups Types of Grading Notebooks -Observations & Data hand- written Lab Reports- TYPED Computer assignments Quizzes Qual Quizzes Possible Extra Credit

7. Looking Ahead Ka, pH, pKa, and Henderson-Hasselbach

8. Equilibrium Constants, K K- tells how well an equilibrium reaction occurs K = [products]/[reactants] aA + bB  cC + dD K = {[C] c [D] d }/{[A] a [B] b } If K is large, then there is more C + D, the equilibrium lies to the right. If K is small, then there is more A + B, the equilibrium lies more to the left.

9. K w Water Dissociation Constant K w = 1.01*10 -14 at 25.00°C H 2 O  H + + OH - K w = [H + ][OH - ]/[H 2 O], [H 2 O]=1 K w = [H + ][OH - ]

10. Acid Dissociation Constant, K a K a – tells how well an acid ionizes in solution HA  H + + A - K a = [H + ][A - ]/[HA] If K is large, then there is more H + + A -, the equilibrium lies to the right. The acid readily dissociates. It is a strong acid. If K is small, then there is more HA, the equilibrium lies more to the left. The acid does not dissociate readily. It is a weak acid.

11. The Henderson-Hasselbach Is it possible to somehow relate the ability to dissociate (strong vs. weak) to pH? Know: pH=-log[H + ], K a = [H + ][A - ]/[HA] Rearrange K a : [H + ] = K a * [HA]/[A - ] Take –log of both sides (definition of pH): -log [H + ] = -log (K a * [HA]/[A - ])=-log((K a ) * ([HA]/[A - ])) For logs, when multiplying add logs, when dividing subtract logs. Apply this rule: -log [H + ] = -log K a -log([HA]/[A - ]) Define: –log K a = pK a, substitute pK a + pH: pH = pK a -log ([HA]/[A - ]) this is the Henderson-Hasselbach equation Now, pH can be related to K a