Chem. 1B – 9/1 Lecture

Welcome to Chem 1BLecture Section 1

• Today’s Meeting– Introduction to Class– Roll Call (only time)– First Day Stuff:

• Printed Handout (not the syllabus)• Materials Needed• Adding this Class• Syllabus• Lab – first two weeks

– Chem 1A Review (very brief)– First Topic: Chemical Equilibria

IntroductionInstructors

• Lecture – Roy Dixon– PhD in Analytical

Chemistry– Research in Environmental

and Analytical Chemistry– Most of my teaching

experience is in teaching Analytical Chemistry

– I have also taught Chem 4 and Chem 1A discussions

– I taught Chem 1B at a previous institution

– Relatively easy going but not easy grading

• Laboratory– most are experienced

Chem 1B instructors– backgrounds in

physical/analytical/inorganic chemistry

Section # Instructor

2 Patrick Sparks

3 Richard Brooks

4 Phillip Marzouk

5 and 6 Katie Smith

7 Heidi Van Atta

IntroductionClass – Main Teaching/Learning Goals

• Lecture – – Topics:

• Equilibrium Related Topics (Chapters 14 – 16)

• Thermodynamics• Electrochemistry• Metal-Ligand Chemistry• Intro to Organic Chemistry

– Besides learning topics, there is an emphasis on:

• Higher level problem solving (can’t just use dimensional analysis)

• Connecting topics to their importance

• Lab– Topics:

• Qualitative Analysis (what ions are in my water?)

• Practical aspects of equilibria (titrations)

• Other topics: thermodynamics, electrochemistry and inorganic chemistry

– Emphasis on:• Report Writing• Working Efficiently

Roll Call(today only)

First Day StuffClass Materials

• Class Handout – summary of materials• Websites for Class

– My faculty website (see handout)– Mastering Site (online chemistry)– SacCT (mainly reporting scores?)– PAL site?

• Text• Lab Manual (1st 37 pages online)• Other Lab Supplies (covered in lab)

First Day StuffAdding This Class

• The Class Size is Limited to 144 (24 students per each of 6 lab sections)

• Adding is done for lab sections– Only can add students to make up for no shows + dropping

students– Priority based on waitlist # (for lab section)– Students must show up to each meeting to stay in class

(notify lab instructor if you can’t make it) or to keep their priority if trying to add

– Most students will be added on second meeting with adding possible in 2nd week to replace dropping students

• Lecture Only– If you are repeating the class and hope to skip the lab, see me

First Day StuffSyllabus – Download from Website• It is your responsibility to read and

understand the complete syllabus. I will go over certain parts, and you can ask questions

• Page 1 notes:– I will post lab instructor office hours– Sequoia 502 is the Help Office (don’t see

instructor there about personal problems)– A C- in Chem 1A is insufficient– Bring a calculator to lecture– Safety equipment is necessary to work in lab

First Day StuffSyllabus – cont.

• Page 2 notes:– Lecture will be strongly focused on problem solving and

conceptual understanding (meant to compliment book learning)

• Page 3 notes:– Lab attendance is required – read if you need to make up

a lab– Grading – breakdowns may be curved downward – but

most likely by only a few % at most and in conjunction with the other section

– Quizzes will be held in the lab but will be split between lecture questions and questions related to pre-lab activities

First Day StuffSyllabus – cont.

• Page 5 notes:– Pay attention to pre-lab assignments and lab report

deadlines– Don’t expect your lab instructor to give you

additional time (past the end time of the lab period)– Disruptions

• You are not required to be in lecture, but• Others are here to learn and can’t pay attention if

disruptions are common

– Help:• help office, other office hours, PALs program, private tutors• have good study habits early

First Day StuffSyllabus – cont.

• Page 6 notes:– If you drop, you also need to check out of lab– Bonus points for student participation (up to 5

points for correct answers)

• Page 7 notes:– Exam dates are not likely to change, but I may get

one lectures behind (so could change exam content)– Homework should match where we are in lecture– See bottom for what you may need to restudy

from Chem 1A

• Page 8 notes: 1st period is M or Tu, 2nd is W or Th

First Day StuffLab – First Two Weeks

• Day 1: yesterday and today– mainly dealing with adding and overview of lab– diagnostic quiz is for you to know which parts

of Chem 1A we expect you to know– read lab manual and understand procedures

(many differences from Chem 1A)

• Day 2: Wed. and Thur.– check in (+ adding students)– review of Chem 1A material (dissolution in

water and solubility)

First Day StuffLab – First Two Weeks

• Day 3: Next Wed. and Thur. (no lab Mon./Tu.)– Pretty extensive pre-lab and then Exp. 1 (over

two lab periods)

Chem 1A ReviewImportant Aspects for Chem 1B

• See Bottom of p. 7 of Syllabus• Chapter 3

- Nomenclature: = the language of chemistry- First, identify substance (molecule, ion, ionic compound,

acid)- ions have charge- molecules vs. ionic compounds: ionic compounds have

cation and anion and almost all cations are metals (NH4+ is

exception)/molecules are all non-metals- molecule name: prefix first element prefix second element

suffix- ionic compound name: metal [oxidation state] anion- anion names: memorize, but only as much as needed

Chem 1A ReviewImportant Aspects for Chem 1B

• Chapter 3 – Nomenclature– How to learn: - memorize (use what

ever technique works for you – e.g. flash cards)

– examples

– ZnCl2 name = _____; type = ________

– OF2 = ____________; type = ________

– CuCl = ___________; type = ________

– Na2SO3 = _________; type = ________

– aluminum chlorite = __; type = ______– nitrous acid = ______; type = ________

= shuĭ = water

Chem 1A ReviewImportant Aspects for Chem 1B

• Chapter 4 - Aqueous Reactions:

- Needed for First Lab- Needed for Chapters 15 and 16 (aqueous equilibria)

- Concepts to Know:- Solution concentration (mainly molarity – how to

calculate)- Dilutions- How substances dissolve into water (differences between

molecules and ionic compounds + acids and bases)- Various reactions (e.g. precipitation, gas evolution, etc.)

+ net ionic equations- Solubility rules

Chem 1A ReviewImportant Aspects for Chem 1B

• Other skill: Problem solving– First determine what the question is asking for– Determine data useful in getting the answer– Map out how to get to the answer

• Chapter 4 – an example problem (more in lab)– A solution is made from 0.202 g of CaCl2 (FW = 110.98 g/mol)

using a 250 mL volumetric flask and deionized water (totally dissolves CaCl2).

– What is the concentration in M?– How does the dissolved compound exist?– What is [Cl-]?– Will any further reactions in water occur?

– If we add AgNO3 to the above solution, what will occur?

Chem 1B First TopicEquilibrium

• In Chapter 13 (near end of Chem 1A), we covered kinetics (how fast reactions occur)

• Past assumption was that “→“ meant reaction went to completion (all products plus limiting reagent)

• Also, unfavorable reactions, such as precipitation of CaCl2 from Ca2+ + Cl- are not supposed to occur at all

• In some important cases, expected reactions will not proceed totally to completion and unexpected reactions can occur to some extent

Chem 1B - EquilibriumIntroduction

• Reactions that can occur in both the forward and reverse reactions to an appreciable extent are represented with a two way arrow:A + B C or A + B ↔ C (easier to type this)

• What does this mean?• From a molecular scale, reactions are occurring

in both the forward and backwards direction• When the forward rate (loss of A to form C) is

equal to the backwards rate (gain of A from C), the system is said to be in equilibrium and concentrations don’t change

Chem 1B - EquilibriumIntroduction

• Graphic example of reaction:A + B ↔ C (assume [A] = [B] at start)In the beginning, forward rate is fast (as A and B are high). At the points the lines cross, [A] = [B] = [C], but the forward rate is still faster than the backwards rate. We can see that [C] is favored over [A] and [B] because its final conc. is higher.

Conc. (A and B)

Conc. (C)

Time

Chem 1B - EquilibriumIntroduction

• Some examples:1. Carbon dioxide (CO2) is not very soluble (you are supposed to know it forms from acid + carbonates)–However, the acidity of rain in “pristine” conditions is supposed to be based on dissolution of CO2:

–CO2 (g) + H2O (l) ↔ H2CO3 (aq) ↔ H+ + HCO3-

2.Nitrogen gas (N2) is difficult to react because of the strength of its triple bonds, however under certain conditions, beneficial and problematic reactions involve N2 where both reactants and products exist.

• N2 (g) + 3H2 (g) ↔ 2NH3 (g) (used in fertilizer)

• N2 (g) + O2 (g) ↔ 2NO (g) (source of smog from combustion)

Conditions are critical to make a) go but to limit b)

Chem 1B - EquilibriumEquilibrium Constant and Equation

• Whether an Equation favors reactants or products is determined by an EQUILIBRIUM CONSTANT (K) – as well as reaction stoichiometry

• Generic reaction: aA + bB ↔ cC + dD• K = equilibrium constant and for above reaction,

• A larger K value means products are more favored

ba

dc

BA

DCK

Chem 1B - EquilibriumEquilibrium Equation – Further Details

• Technically, instead of concentration we have a concentration ratio to a “standard state” (e.g. 1 mol/L) – we can ignore this, but this is why K is unitless

• Only species in gas phase or in solution will have concentrations. Solids and pure liquids are not included.

• When gases are involved, there are two Ks: KC for concentration units (including gases) and KP in which pressure (atm) replaces concentration (assume K = KC unless specified)

• Even further corrections (activity and fugacity) are needed under certain conditions but are beyond this class

Chem 1B - EquilibriumEquilibrium Equation – Example

• N2 (g) + O2 (g) ↔ 2NO (g)

or

At T = 25°C KC = KP(in this case) = 4 x 10-31

an insignificant amount of NO will form in air: PN2 = 0.8 atm , PO2 = 0.2 atm; rearranging the above equation, PNO = [KPPN2PO2]0.5 = 2 x 10-16 atm

Equilibrium at room temp. is not realistic because kinetics is too slow (insufficient collision energy to break triple bond)

At car engine temp., reactions are faster and K is much larger. This leads to significant NO formation. Fuel rich conditions (low PO2 ) can limit NO formation.

22

2

ON

NOKC

22

2

ON

NOP PP

PK