CHEM 200/202. Professor Gregory P. Holland Office: GMCS-213C. All s are to be sent to:

Transcription

1 CHEM 200/202 Professor Gregory P. Holland Office: GMCS-213C All s are to be sent to: My office hours will be held in GMCS-212 on Monday from 12:00 pm to 2:00 pm or by appointment.

2 ONLINE TOOLS Blackboard: one section for each lab. Links on sidebar to various resources: OWL - online homework and quizzes ebook - a pdf version of the book chemistry New website this semester: sdsuchem200.com

3 SUPPLEMENTAL INSTRUCTION Occur 15 times a week. Free to access, no reporting to faculty. Link to the SI schedule is on blackboard.

4 ANNOUNCEMENTS Waitlisters: Sections (Gu s Labs), My Lecture, If you have class at 2 PM. We will be able to accommodate you (check ) - drop add is over If you were waitlisted and got in, chem200@mail.sdsu.edu In OWL watch the tutorials prior to doing any assignments (WE KNOW IF YOU HAVE NOT WATCHED THEM), Getting Started with OWL Note: OWL Assignments are due by 11:55 PM on due date, pre-assignments and pre-lab 8 AM on Mondays (2 Owl sections, HW & Labs)

5 HOMEWORK & EXAM 1(CHAPTERS 1-4) Homework 2 due 2/2 (this Friday) Quiz 1 due 2/8 (next Thursday) Homework 3 due 2/9 (next Friday) Homework 4 due 2/9 (next Friday) Exam 1 is Saturday 2/10 at 2 PM (Review 2/9)

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7 LECTURE OBJECTIVES Chapter 3.3 Molarity Calculate solution concentrations using molarity. Perform dilution concentrations. Chapter 3.4 Other Units For solution Concentrations. Weight %, volume %, parts per million (ppm) and parts per billion (ppb) Chapter 4.1 Writing and Balancing Chemical Equations. Write and balance chemical equations in molecular, total ionic and net ionic formats. Chapter 4.2 Classifying Chemical Reactions. Define 3 types of chemical reactions (precipitation, acid-base, oxidation-reduction). Predict solubility of common inorganic compounds by using solubility rules. Compute the oxidation states for elements in compounds.

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10 CONCENTRATED & DILUTE SOLUTIONS Concentrated solutions have more solute per unit volume than dilute solutions. Concentrated solutions can be made dilute by adding more solvent. Dilute solutions can be made more concentrated by adding more solute, or by removing (selectively) more solvent.

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12 QUESTION Take ml of a M KMnO4 solution. Dilute the ml solution to L with water. What is the molarity of the resulting solution? M KMnO4

13 OTHER UNITS OF CONCENTRATION Concentrations are used to express the amount of solute in a solution, this can be done in more ways than just molarity (mol/l). Mass percent (w/w%) Volume percent (v/v%) Mass-volume percent (w/v%) Parts per million (ppm) and parts per billion (ppb)

14 EXPRESSING CONCENTRATION IN PERCENTAGES The expression of concentration as a percentage is very similar to how percentage grades are expressed. The key is to use the proper units for each calculation. Mass percent (w/w%) Volume percent (v/v%) ppm and ppb mass percentage = mass of component mass of solution 100 ted in the mass percentages of solutes, but it is also p volume percentage = volume solute volume solution 100 ppm = ppb = mass solute mass solution 106 ppm mass solute mass solution 109 ppb

15 MASS % PROBLEM A throat spray is 1.40% by mass phenol, C6H5OH, in water. If the solution has a density of g/ml, calculate the molarity of the solution.

16 PPM/PPB PROBLEM The EPA monitors lead (Pb) in tap water to ensure that it does not exceed 15 ppb. What is this concentration in ppm? At this concentration what mass of lead (in µg) would be contained in a typical glass of water (300. ml)? The density of water is 1.00 g/ml.

17 CHAPTER 4 STOICHIOMETRY OF CHEMICAL REACTIONS

18 REACTION CLASSIFICATIONS There are three principle aqueous chemical reactions that we will focus on in this course: Precipitation reactions Acid-Base reactions Redox reactions (oxidation-reduction)

19 EQUATIONS FOR AQUEOUS IONIC REACTIONS Molecular equation: shows all the reactants and products as intact, undissociated compounds (sometimes we will be required to balance the chemical equation first). Ionic equation: shows all the soluble ionic substances dissociated into ions. Net ionic equation: eliminates the spectator ions and shows the actual chemical change that takes place.

20 NET IONIC EQUATIONS Steps: Write the balanced molecular equation - you may have to predict the products of the reaction. Ionize all strong electrolytes in solution. Cancel all spectator ions. Write the leftover species.

21 PRECIPITATION REACTIONS Precipitation reactions occur when pairs of insoluble ions (e.g. Ag + and Cl - ) both present in solution at the same time. A mixture of aqueous solutions may result in more than one precipitate being formed, if more than one insoluble pair is present. Knowledge of the common soluble and insoluble ions is required to predict precipitations (The Solubility Rules).

22 Soluble SOLUBILITY RULES 1. All common compounds of Group 1A(1) ions (Li +, Na +, K +...) and ammonium ions (NH4 + ) 2. All common nitrates (NO3 - ), acetates (CH3CO2 - ) and most perchlorates (ClO4 - ) 3. All common chlorides (Cl - ), bromides (Br - ) and iodides (I - ); except those of Ag +, Pb 2+, Cu + and Hg2 2+. All common fluorides (F - ) are soluble; except for Pb 2+ & Group2A(2) 4. All common sulfates (SO4 2- ); except Ca 2+, Sr 2+, Ba 2+, Ag + & Pb 2+

23 Insoluble SOLUBILITY RULES 1) All common metal hydroxides are insoluble; except those of Group 1A(1) and the larger members of Group 2A(2) - beginning with Ca 2+. 2) All common carbonates (CO3 2- ), phosphates (PO4 3- ) and chromates (CrO4 2- ) are insoluble; except those from Group 1A(1) and ammonium (NH4 + ). 3) All common sulfides (S 2- ) are insoluble; except those of Groups 1A(1), 2(A)2 and NH4 +.

24 PREDICTING PRECIPITATION 1. Note the ions present in the reactants. 2. Consider the possible cation-anion combination. 3. Decide wether any of the ion combinations is insoluble and thus, form a precipitate.

25 ACIDS AND BASES Acids - produce H + (aq) when dissolved in water Bases - produce OH - (aq) when dissolved in water Strong acid/base - completely dissociates in water Weak acid/base - incompletely dissociates in water

26 ACIDS Monoprotic: one ionizable hydrogen HCl + H2O H3O + + Cl - Diprotic: two ionizable hydrogens H2SO4 + H2O H3O + + HSO4 - HSO4 - + H2O H3O + + SO4 2- Triprotic: three ionizable hydrogens Polyprotic, generic term meaning that there is more than one ionizable hydrogen on the molecule. H3PO4 + H2O H3O + + H2PO4 - H2PO4 - + H2O H3O + + HPO4 2- HPO H2O H3O + + PO4 3-

27 BASES Monobasic: yields one OH - ion KOH K + + OH - NH3 +H2O NH4 + + OH - Dibasic: yields two OH - ions Ba(OH)2 Ba OH - Ca(OH)2 Ca OH -

28 SELECTED ACIDS & BASES Strong Acids Hydrochloric acid, HCl Hydrobromic acid, HBr Hydroiodic acid, HI Nitric acid, HNO3 Sulfuric acid, H2SO4 Perchloric acid, HClO4 Weak Acids Hydrofluoric acid, HF Phosphoric acid, H3PO4 Acetic acid, CH3COOH (or HC2H3O2) Strong Bases Sodium hydroxide, NaOH Potassium hydroxide, KOH Calcium hydroxide, Ca(OH)2 Strontium hydroxide, Sr(OH)2 Barium hydroxide, Ba(OH)2 Weak Bases Ammonia, NH3

29 ACID-BASE NEUTRALIZATION Acid + Base Water + Salt Molecular equation Total ionic equation HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq) H + (aq) + Cl - (aq) + Na + (aq) + OH - (aq) H2O(l) + Na + (aq) + Cl - (aq) Net ionic equation H + (aq) + OH - (aq) H2O(l) Hint: Balance the H + with OH - the rest will work itself out.

30 AN AQUEOUS STRONG ACID-BASE REACTION ON THE ATOMIC SCALE