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Chemistry Lab

Chemistry Lab. By Lin Wozniewski lwoz@iun.edu. Disclaimer. This presentation was prepared using draft rules.  There may be some changes in the final copy of the rules.  The rules which will be in your Coaches Manual and Student Manuals will be the official rules.

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Chemistry Lab

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  1. Chemistry Lab By Lin Wozniewski lwoz@iun.edu

  2. Disclaimer This presentation was prepared using draft rules.  There may be some changes in the final copy of the rules.  The rules which will be in your Coaches Manual and Student Manuals will be the official rules

  3. Interpretation of experimental data (tabular and/or graphic) Observation of an experiment set up and running Computer or calculator sensors/probes Stoichiometry : mole conversions and percentage yield Nomenclature and formula writing - symbols and charges for the following ions by memory: nitrate, carbonate, phosphate, acetate, sulfate, ammonium, bicarbonate, and hydroxide (“ite” forms of “ates” listed) What do they need to be able to do every year every year?

  4. Safety • Students must wear: • Closed shoes • All skin from neck to toes covered • Lab coat or lab apron • Indirect vent or unvented chemical splash proof goggles. • All skin from neck to wrists covered • Long hair (shoulder length or longer) must be tied back. • Visorgogspermitted

  5. What the Students Should Bring • Safety gear • Something to write with • One (1) 8.5 X 11” sheets of paper, two sided containing information in any form from any sourceper team • One non image capable calculator per student. • Chemistry C Kit

  6. Chemistry C Kit Beakers Spot Plates Test Tubes Test Tube holders Test Tube brushes Test Tube clamps Graduated cylinders, 10 ml, or 25 ml Stir rods Calipers-mechanical, not digital Nail, Zn, and Cu metal pieces

  7. Chemistry C Kit Continued Funnels Filter paper pH paper Flame loop Cobalt blue glass Paper towels Forceps or Metal Tongs Hand lens Pencil Thermometer

  8. Chemistry C Kit Continued Microspatula or scoopula Eye droppers Ruler Battery Conductivity meter Slides & cover slips Battery multimeter Alligator clip wires Petri Dishes Erlenmeyer Flasks

  9. What the Supervisor Provides • Everything the student will need • This may include: • Glassware not included in the kit • Reagents • Balances • Hot plates • Probes • Magnets • Stirrers

  10. How to prepare participants • Make sure students read the directions and pay particular attention to the description of the event (The Competition) • Have them do many experiments together • Have them determine their individual strengths • Divide (and conquer) tasks during competition • Check each other’s work

  11. How to prepare participants • Get as many lab books from your chemistry teacher as possible & have students explore labs by topic and do the ones that appear consistently

  12. The modern periodic table. Figure 2.10

  13. Elements that occur as molecules. Figure 2.16 diatomic molecules tetratomic molecules octatomic molecules

  14. Some common monatomic ions of the elements. Figure 2.19 Can you see any patterns?

  15. Stoichiometry • Know that reactions relate moles of reactant to moles of product. • Be able to do mole conversions

  16. PROBLEM: amount(mol) of Ag 107.9 g Ag mass(g) of Ag mol Ag mass(g) of Fe amount(mol) of Fe mol Fe 55.85g Fe 6.022x1023atoms Fe atoms of Fe mol Fe Sample Problem 3.1 Calculating the Mass and the Number of Atoms in a Given Number of Moles of an Element (a) Silver (Ag) is used in jewelry and tableware but no longer in U.S. coins. How many grams of Ag are in 0.0342mol of Ag? (b) Iron (Fe), the main component of steel, is the most important metal in industrial society. How many Fe atoms are in 95.8g of Fe? PLAN: (a) To convert mol of Ag to g we have to use the #g Ag/mol Ag, the molar mass M. multiply by M of Ag (107.9g/mol) SOLUTION: = 3.69g Ag 0.0342mol Ag x PLAN: (b) To convert g of Fe to atoms we first have to find the #mols of Fe and then convert mols to atoms. divide by M of Fe (55.85g/mol) SOLUTION: 95.8g Fe x = 1.72mol Fe multiply by 6.022x1023 atoms/mol = 1.04x1024 atoms Fe 1.72mol Fe x

  17. Balancing Chemical Equations translate the statement balance the atoms adjust the coefficients check the atom balance specify states of matter

  18. PLAN: SOLUTION: 2C8H18 + 25O216CO2 + 18H2O C8H18 + O2 CO2 + H2O C8H18 + O2 CO2 + H2O 2C8H18 + 25O216CO2 + 18H2O balance the atoms adjust the coefficients check the atom balance 2C8H18(l) + 25O2 (g) 16CO2 (g) + 18H2O (g) specify states of matter Sample Problem 3.7 Balancing Chemical Equations PROBLEM: Within the cylinders of a car’s engine, the hydrocarbon octane (C8H18), one of many components of gasoline, mixes with oxygen from the air and burns to form carbon dioxide and water vapor. Write a balanced equation for this reaction. translate the statement 25/2 8 9

  19. SiO2(s) + 3C(s) SiC(s) + 2CO(g) 103 g SiO2 mol SiO2 kg SiO2 60.09 g SiO2 40.10 g SiC kg mol SiC 103g 51.4 kg 66.73 kg Sample Problem 3.12 Calculating Percent Yield PROBLEM: Silicon carbide (SiC) is an important ceramic material that is made by allowing sand(silicon dioxide, SiO2) to react with powdered carbon at high temperature. Carbon monoxide is also formed. When 100.0 kg of sand is processed, 51.4 kg of SiC is recovered. What is the percent yield of SiC from this process? PLAN: SOLUTION: write balanced equation 100.0 kg SiO2 = 1664 mol SiO2 find mol reactant & product mol SiO2 = mol SiC = 1664 find g product predicted 1664 mol SiC = 66.73 kg actual yield/theoretical yield x 100 percent yield x100 =77.0%

  20. Cations Anions Formula Name Formula Name Charge Charge H+ hydrogen H- hydride Li+ lithium F- fluoride Na+ sodium Cl- chloride K+ potassium Br- bromide Cs+ cesium I- iodide Ag+ silver Mg2+ magnesium O2- oxide Ca2+ calcium S2- sulfide Sr2+ strontium Ba2+ barium Zn2+ zinc Cd2+ cadmium Al3+ aluminum N3- nitride Table 2.3 Common Monoatomic Ions Common ions are in red. +1 -1 +2 -2 +3 -3

  21. Naming binary ionic compounds The name of the cation is written first, followed by that of the anion. The name of the cation is the same as the name of the metal. Many metal names end in -ium. The name of the anion takes the root of the nonmetal name and adds the suffix -ide. Calcium and bromine form calcium bromide.

  22. PROBLEM: Name the ionic compound formed from the following pairs of elements: Sample Problem 2.5 Naming Binary Ionic Compounds (a) magnesium and nitrogen (b) iodine and cadmium (c) strontium and fluorine (d) sulfur and cesium PLAN: Use the periodic table to decide which element is the metal and which the nonmetal. The metal (cation) is named first and we use the -ide suffix on the nonmetal name root. SOLUTION: (a) magnesium nitride (b) cadmium iodide (c) strontium fluoride (d) cesium sulfide

  23. CO3-2 carbonate acetate CH3COO- CrO4-2 chromate CN- cyanide OH- hydroxide Cr2O7-2 dichromate chlorate ClO3- O2-2 peroxide NO2- nitrite SO4-2 sulfate PO4-3 NO3- nitrate phosphate SO3-2 sulfite Some Common Polyatomic Ions Table 2.5 (partial) Formula Formula Name Name Cations H3O+ hydronium ammonium NH4+ Common Anions HCO3- bicarbonate

  24. Types of Chemical Bonding 1. Metal with nonmetal: electron transfer and ionic bonding 2. Nonmetal with nonmetal: electron sharing and covalent bonding 3. Metal with metal: electron pooling and metallic bonding

  25. A general comparison of metals and nonmetals. Figure 9.1

  26. Writing Equations for Aqueous Ionic Reactions The molecular equation shows all of the reactants and products as intact, undissociated compounds. The total ionic equation shows all of the soluble ionic substances dissociated into ions. The net ionic equation eliminates the spectator ions and shows the actual chemical change taking place.

  27. Soluble Ionic Compounds Insoluble Ionic Compounds Table 4.1 Solubility Rules For Ionic Compounds in Water 1. All common compounds of Group 1A(1) ions (Li+, Na+, K+, etc.) and ammonium ion (NH4+) are soluble. 2. All common nitrates (NO3-), acetates (CH3COO- or C2H3O2-) and most perchlorates (ClO4-) are soluble. 3. All common chlorides (Cl-), bromides (Br-) and iodides (I-) are soluble, except those of Ag+, Pb2+, Cu+, and Hg22+. 1. All common metal hydroxides are insoluble, except those of Group 1A(1) and the larger members of Group 2A(2)(beginning with Ca2+). 2. All common carbonates (CO32-) and phosphates (PO43-) are insoluble, except those of Group 1A(1) and NH4+. 3. All common sulfides are insoluble except those of Group 1A(1), Group 2A(2) and NH4+.

  28. Sample Problem 4.3 Predicting Whether a Precipitation Reaction Occurs; Writing Ionic Equations PROBLEM: Predict whether a reaction occurs when each of the following pairs of solutions are mixed. If a reaction does occur, write balanced molecular, total ionic, and net ionic equations, and identify the spectator ions. (a) sodium sulfate(aq) + strontium nitrate(aq) (b) ammonium perchlorate(aq) + sodium bromide(aq) SOLUTION: PLAN: (a) Na2SO4(aq) + Sr(NO3)2 (aq) 2NaNO3(aq) + SrSO4(s) write ions 2Na+(aq) +SO42-(aq)+ Sr2+(aq)+2NO3-(aq) 2Na+(aq) +2NO3-(aq)+ SrSO4(s) combine anions & cations SO42-(aq)+ Sr2+(aq) SrSO4(s) check for insolubility Table 4.1 (b) NH4ClO4(aq) + NaBr(aq) NH4Br(aq) + NaClO4(aq) eliminate spectator ions for net ionic equation All reactants and products are soluble so no reaction occurs.

  29. Table 4.2 Selected Acids and Bases Acids Bases Strong Strong hydrochloric acid, HCl sodium hydroxide, NaOH hydrobromic acid, HBr potassium hydroxide, KOH hydroiodic acid, HI calcium hydroxide, Ca(OH)2 nitric acid, HNO3 strontium hydroxide, Sr(OH)2 sulfuric acid, H2SO4 barium hydroxide, Ba(OH)2 perchloric acid, HClO4 Weak Weak hydrofluoric acid, HF ammonia, NH3 phosphoric acid, H3PO4 acetic acid, CH3COOH (or HC2H3O2)

  30. (a) strontium hydroxide(aq) + perchloric acid(aq) (b) barium hydroxide(aq) + sulfuric acid(aq) PLAN: reactants are strong acids and bases and therefore completely ionized in water (a) Sr(OH)2(aq)+2HClO4(aq) 2H2O(l)+Sr(ClO4)2(aq) products are 2OH-(aq)+ 2H+(aq) 2H2O(l) water (b) Ba(OH)2(aq) + H2SO4(aq) 2H2O(l) + BaSO4(aq) spectator ions 2OH-(aq)+ 2H+(aq) 2H2O(l) Sample Problem 4.4 Writing Ionic Equations for Acid-Base Reactions PROBLEM: Write balanced molecular, total ionic, and net ionic equations for each of the following acid-base reactions and identify the spectator ions. SOLUTION: Sr2+(aq) + 2OH-(aq)+ 2H+(aq)+ 2ClO4-(aq) 2H2O(l)+Sr2+(aq)+2ClO4-(aq) Sr2+(aq) + 2OH-(aq)+ 2H+(aq)+ 2ClO4-(aq) 2H2O(l)+Sr2+(aq)+2ClO4-(aq) Ba2+(aq) + 2OH-(aq)+ 2H+(aq)+ SO42-(aq) 2H2O(l)+Ba2+(aq)+SO42-(aq)

  31. General rules Rules for specific atoms or periodic table groups 1. For Group 1A(1): O.N. = +1 in all compounds 2. For Group 2A(2): O.N. = +2 in all compounds 3. For hydrogen: O.N. = +1 in combination with nonmetals 4. For fluorine: O.N. = -1 in combination with metals and boron 5. For oxygen: O.N. = -1 in peroxides O.N. = -2 in all other compounds(except with F) 6. For Group 7A(17): O.N. = -1 in combination with metals, nonmetals (except O), and other halogens lower in the group Table 4.3 Rules for Assigning an Oxidation Number (O.N.) 1. For an atom in its elemental form (Na, O2, Cl2, etc.): O.N. = 0 2. For a monoatomic ion: O.N. = ion charge 3. The sum of O.N. values for the atoms in a compound equals zero. The sum of O.N. values for the atoms in a polyatomic ion equals the ion’s charge.

  32. Figure 4.12 Highest and lowest oxidation numbers of reactive main-group elements.

  33. PROBLEM: Determine the oxidation number (O.N.) of each element in these compounds: Sample Problem 4.6 Determining the Oxidation Number of an Element (a) zinc chloride (b) sulfur trioxide (c) nitric acid PLAN: The O.N.s of the ions in a polyatomic ion add up to the charge of the ion and the O.N.s of the ions in the compound add up to zero. SOLUTION: (a) ZnCl2. The O.N. for zinc is +2 and that for chloride is -1. (b) SO3. Each oxygen is an oxide with an O.N. of -2. Therefore the O.N. of sulfur must be +6. (c) HNO3. H has an O.N. of +1 and each oxygen is -2. Therefore the N must have an O.N. of +5.

  34. Changes for 2016 • 1 new topic & 1 old topic: • Acid Base • Physical Properties

  35. Acid Base • Students will complete experimental tasks and answer questions related to acid-base chemistry. Students may be expected to complete labs/activities such as: • (1) Properties & Uses of Common Acids (HCl, HNO3, H2SO4, H3PO4, H2CO3, acetic and ascorbic acid) and Bases (NaOH, KOH, Ca(OH)2, Mg(OH)2, and NH3(aq)) • (2) Acid/Base indicators (pH ranges and color changes will be provided). Use of indicators, NOT theory of how they work, is the emphasis. Reactions of acids and bases will be limited to metals, carbonates, bicarbonates, sulfites, bisulfites, oxides, and neutralization reactions: • (3) Titrations to determine percent composition, molarity, and/or molecular mass. • (4) Additional calculations will be limited to Ka, Kb, pH, pOH, and dilution. Calculations or questions about buffers will only be included at the state or national levels.

  36. Physical Properties

  37. Physical Properties Students should understand the following concepts: density; color; conductivity; boiling & melting points; electrical resistance; elasticity / brittle, not brittle; heat capacity; specific heat; solubility; magnetism; extensive (amount of matter) & intensive (type of matter) properties. Activities may include: Determination of the density of an object, use density to identify an unknown metal, determination of the density of a liquid using a pycnometer, separation a mixture by physical properties (magnetism, solubility,etc.), exploration of the effect of temperature on solubility, determination of melting point of a substance.

  38. Matter anything that has mass and volume -the “stuff” of the universe: books, planets, trees, professors, students Composition the types and amounts of simpler substances that make up a sample of matter Properties the characteristics that give each substance a unique identity Definitions Physical Properties those which the substance shows by itself without interacting with another substance such as color, melting point, boiling point, density Chemical Properties those which the substance shows as it interacts with, or transforms into, other substances such as flammability, corrosiveness

  39. Table 1 SI Base Units time second s temperature kelvin K electric current ampere A amount of substance mole mol luminous intensity candela cd Physical Quantity (Dimension) Unit Abbreviation Unit Name mass kilogram kg length meter m

  40. Table 2 Common Decimal Prefixes Used with SI Units

  41. Common SI-English Equivalent Quantities Table 3 1 kilometer(km) 1000(103)m 0.62miles(mi) 1 mi = 1.61km 1 meter(m) 100(102)cm 1000(103)mm 1.094yards(yd) 39.37inches(in) 1 yd = 0.9144m 1 foot (ft) = 0.3048m 1 centimeter(cm) 0.01(10-2)m 0.3937in 1 in = 2.54cm (exactly!) 1 kilometer(km) 1000(103)m 0.62mi Quantity SI Unit SI Equivalent English Equivalent Length English to SI Equivalent

  42. Common SI-English Equivalent Quantities Table 4 1 cubic meter(m3) 1,000,000(106) cubic centimeters 35.2cubic feet (ft3) 1 ft3 = 0.0283m3 1 cubic decimeter(dm3) 1000cm3 0.2642 gallon (gal) 1.057 quarts (qt) 1 gal = 3.785 dm3 1 qt = 0.9464 dm3 1 cubic centimeter (cm3) 0.001 dm3 0.0338 fluid ounce 1 qt = 946.4 cm3 1 fluid ounce = 29.6 cm3 Quantity SI Unit SI Equivalent English Equivalent Volume English to SI Equivalent

  43. PROBLEM: The volume of an irregularly shaped solid can be determined from the volume of water it displaces. A graduated cylinder contains 19.9mL of water. When a small piece of galena, an ore of lead, is submerged in the water, the volume increases to 24.5mL. What is the volume of the piece of galena in cm3 and in L? subtract 1 cm3 10-3 L mL mL 1 mL = 1 cm3 1 mL = 10-3 L Sample Problem 1 Converting Units of Volume PLAN: The volume of galena is equal to the change in the water volume before and after submerging the solid. SOLUTION: volume (mL) before and after addition (24.5 - 19.9)mL = volume of galena volume (mL) of galena 4.6 mL x = 4.6 cm3 volume (cm3) of galena volume (L) of galena 4.6 mL x = 4.6x10-3 L

  44. PROBLEM: International computer communications are often carried by optical fibers in cables laid along the ocean floor. If one strand of optical fiber weighs 1.19 x 10-3lbs/m, what is the total mass (in kg) of a cable made of six strands of optical fiber, each long enough to link New York and Paris (8.84 x 103km)? 8.84 x 103km x 1 km = 103 m 8.84 x 106m x 103m 1.19 x 10 -3lbs 1 m = 1.19x10-3 lb 6.30x 104lb 6 fibers km m = 1.05 x 104lb x cable cable 6 fibers = 1 cable 6.30x 104lb 1kg 2.86x104 kg x = cable cable 2.205 lb 2.205 lb = 1 kg Sample Problem 2 Converting Units of Mass PLAN: The sequence of steps may vary but essentially you have to find the length of the entire cable and convert it to mass. SOLUTION: length (km) of fiber = 8.84 x 106m length (m) of fiber = 1.05 x 104lb mass (lb) of fiber mass (lb) of cable mass (kg) of cable

  45. Figure 1 Some interesting quantities. A Length B Volume C Mass

  46. Densities of Some Common Substances* Table 5 Hydrogen Gas 0.0000899 Oxygen Gas 0.00133 Grain alcohol Liquid 0. 789 Water Liquid 0.998 Table salt Solid 2.16 Aluminum Solid 2.70 Lead Solid 11.3 Gold Solid 19.3 Substance Physical State Density (g/cm3) *At room temperature(200C) and normal atmospheric pressure(1atm).

  47. PROBLEM: Lithium (Li) is a soft, gray solid that has the lowest density of any metal. If a slab of Li weighs 1.49 x 103 mg and has sides that measure 20.9 mm by 11.1 mm by 11.9 mm, what is the density of Li in g/cm3 ? 10 mm = 1 cm 1cm 10mm 103 mg = 1 g multiply lengths 10-3g 1mg 1.49g 2.76 cm3 Sample Problem 2 Calculating Density from Mass and Length PLAN: Density is expressed in g/cm3 so we need the mass in grams and the volume in cm3. SOLUTION: lengths (mm) of sides 1.49x103mg x = 1.49g mass (mg) of Li lengths (cm) of sides 20.9mm x = 2.09cm Similarly the other sides will be 1.11 cm and 1.19 cm, respectively. mass (g) of Li volume (cm3) 2.09 x 1.11 x 1.20 = 2.76cm3 density (g/cm3) of Li density of Li = = 0.540 g/cm3

  48. The freezing and boiling points of water. Figure 1.12

  49. Figure 5 Some interesting temperatures.

  50. Temperature Scales and Interconversions Kelvin ( K ) - The “Absolute temperature scale” begins at absolute zero and only has positive values. Celsius ( oC ) - The temperature scale used by science, formally called centigrade, most commonly used scale around the world; water freezes at 0oC, and boils at 100oC. Fahrenheit ( oF ) -Commonly used scale in the U.S. for our weather reports; water freezes at 32oF and boils at 212oF. T (in K) = T (in oC) + 273.15 T (in oC) = T (in K) - 273.15 T (in oF) = 9/5 T (in oC) + 32 T (in oC) = [ T (in oF) - 32 ] 5/9

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