Benchmark 2 Review

Benchmark 2 ReviewPercent CompositionPercent Composition percentage by mass of each element in the cmpd

From sample amts:Mass of element in sample X 100=% E in compound mass of sample

PropertiesChemists use properties to distinguish between substances and to separate them. By comparing several properties of a subst, an unknown substance can be identified. PropertiesExtensive property- depend on the amount matter such as mass

Intensive property- does not depend on the amount of matter, such as odor.Physical PropertiesPhysical Properties- can be observed or measured without changing the identity of the substEx. Observing and measuring the boiling pt of water

Physical Change- a change that doesnt involve changing the identity of the substEx. Liquid water changing to water vapor when boiledPhysical States of MatterSolid- definite shape and volume. Particles tightly packed in fixed positions and can only vibrate.

Liquid- definite volume, indefinite shape. Particles can flow past each other (fluid)

Gas- indefinite shape, indefinite volume, fluid. Particles move more rapidly with lots of space in between. Particles take up volume and shape of container

Plasma- high temperature matter where atoms lose their electrons. Ex. The sun

Chemical PropertiesChemical Properties- substance's ability to undergo changes to form new substances Ex: ability of iron to react with oxygen to form rustPeriodic TableGroups or Families - vertical columns of elements in the periodic table. Numbered 1-18 OR with A/B system

Periods - horizontal rows of elements in the periodic table. Numbered 1-7

Ex. Ge is located in group _____ and period _____

Metals and NonmetalsThe periodic table is divided into two main sections: Metals and Nonmetals

Metals elements that are: Ex. Cu, Ni, Al good conductors of electricity and heatsolids at room temp with lusterductile (drawn into wires)malleable (hammered into sheets) tensile strength (resist breaking when pulled)

Nonmetalselements that are :Poor conductors of heat and electricityMany gasesBrittle

Ex. C, O, S

MetalloidsElements with characteristics of both metals and nonmetalsEx. Si conducts electricity at high temp, not low temp; used as a semiconductor for computers

Noble GasesNoble Gases- elements in Grp 18 (8A) that are generally nonreactive

Ex. He, Ne, Ar

Section Review p. 24Dmitri MendeleevDmitri Mendeleev developed the periodic table in 18691. He grouped elements with similar chemical and physical properties together2. He arranged the elements in increasing atomic mass.3. He predicted the properties of elements not yet discovered.Periodic TableTodays periodic table, the elements are arranged in increasing atomic number so elements with similar properties fall in the same group. Note: Ar and K both in according to atomic number, not atomic mass

Periodic LawPeriodic Law: When elements are arranged in increasing atomic numbers, there is a repeating (periodic) pattern to the properties. See tables p. 142, 144, 148, 152.

Group NamesGroup 1 elements Alkali Metals Very, very reactive metalsGroup 2 elements Alkaline Earth Metals Very reactive metalsGroup 17 elements Halogens Very reactive nonmetalsGroup 18 elements Noble gases Nonreactive elementsTransition MetalsGroup 3 to 12 Transition MetalsTypical metals

Inner Transition Elements : lower two rows detached from main tableLanthanides atomic numbers from 58 to 71Actinides atomic numbers from 90 to 103

Blocks of ElementsS-block elements- valence electrons are filling the s orbitals- Groups 1-2

D-block elements-valence electrons are filling the d orbtials- Groups 3-12

P-block elements-valence electrons are filling the p orbitals- Groups 13-18 except He

F-block elements-valence electrons are filling the f orbitals- Lanthanide and Actinide

Periodic TrendsAtomic Radii the distance between the nuclei of 2 of the same atoms bonded together.

Atomic radii trends:Going across a period atoms get smaller caused by increasing positive charge.Going down a group atoms get larger adding energy level

Prac P.142IonsIon is an atom with a positive or negative charge. Cation formed by loss of electron(s) and has a positive charge. Anion formed by gain of electron(s) and has a negative charge. Illustrate example of atom, cation, and anion.Ionic RadiiIonic radii positive ions are smaller than neutral atom due to loss of electron negative ions are larger than neutral atom due to gain of electron

Ionic radii trends: same as atomic radii patternsGoing across a period atoms get smaller Going down a group atoms get larger Ionization EnergyIonization energy (IE) energy it takes to remove an electron from a neutral atom

IE trends: Going across period IE increases greater positive to negative attraction, harder to remove electronGoing down a group IE decreases easier to remove an electron because it is farther from the nucleusElectronegativityElectronegativity measure of the ability of an atom to attract electrons to itself

Electronegativity trends:Going across a period increase more positive charge in nucleus in same energy levelGoing down a group decrease nuclear attraction decrease with distance from nucleus

Prac P.152 and section review p.154FormulasEmpirical Formula smallest whole number ratio of atoms in a compd.Ex. HCl, H2O

Molecular Formula actual formula of a molecule of compd some multiple of the empirical formulaEx. HCl, C2H4Determining Empirical Formulas from Quantitative Analysis:

Convert % info to grams.Convert grams to moles of elementGet whole number ratios by dividing by smallest # of moles.Molecular FormulaCalculation of Molecular Formula:x(EF) = MF

MF mass = x EF mass

Problem must provide the molar mass of the compd from experimental data.

Measurements and CalculationsChapter 2Units of MeasurementsA quantity must have magnitude, size, or amount.

All scientist agree to use the same measurement system the SI system.SI Base Units memorize these p34Quantity, symbolUnit, abbrev.

Length, lmeter, mMass, mkilogram, kgTemperature, TKelvin, KAmt of substance, nmole, molTime, tsecond, sSI Prefixes memorize these pg35PrefixAbbrevExpon. FactorMemorize this:GigaG109Gm = 109MegaM106Mm = 106Kilok103km = 103Hectoh102Hm = 102DekaDa101Dam = 1011001 mdecid10-1dm = 10-1centic10-2cm = 10-2Millim10-3mm = 10-3Microu10-6um = 10-6Nanon10-9nm = 10-9 Picop10-12pm = 10-12Derived unitsDerived units units obtained from a calculationArea, A, m2 derived by: l x w

Volume, V, m3, derived by: l x w x h. We will also use non-SI volume unit of liter, LMemorize: one liter = one decimeter cubed (1 L = 1 dm3) one milliliter = one centimeter cubed (1 mL=1 cm3)

Derived unitsDensity, D, kg/m3, derived by mass divided by volumeD = M VProb: 1. A 8.4 g sample of aluminum metal has a volume of 3.1 cm3. Calculate the density of aluminum.DensityDetermine the volume of a 76.4 g sample of liquid mercury that has a density of 13.6 g/mL?

Prac p.40; section review p.42Conversion FactorConversion factor is a ratio of equivalents of different units.Every conversion factor has a value of 1.

Ex. 12 inches10-6 m 1 foot 1 umConversion FactorProb. Write these into a conversion factor.12 grams of copper are needed for every two students.A conversion factor between mg and g.A conversion factor between kL and L.

Dimensional AnalysisDimensional analysis solving problems for the correct units as well as numbers. It is a way to help you set up the correct equation to solve the problem.

Steps to solve dimensional analysis problemWrite given on left.Set conversion factor so given unit will cancel. Base unit gets the number 1.Solve.Scientific MeasurementsAccuracy closeness to the accepted value or correct value

Precision closeness of a set of measurements to each other

Look at dart examples p.44Illustrate your own example of 5 quiz grades that have:High accuracy, high precisionLow accuracy, high precisionLow accuracy, low precisionPercent ErrorPercent error = valueaccepted valueexperimental * 100valueaccepted

Problem: A student measures the mass of an object to be 4.80 g and the volume to be 3.2 mL. The actual density is 1.36 g/mL. What is the percent error of the students measurements?

Practice p.45Significant FiguresSee fig 2-9 on p46. Which value would be appropriate to record for the measurement? 6.3623678945678564 or 6.36 cm? Measurements in science are recorded in terms of significant figures to show the amount of certainty we have with the numbers that are being measured.Significant FiguresSignificant Figures a measurement with known digits and one estimated digit

Rules to determine sign. fig.Non-zero numbers are significant.Count all zeros between nonzero numbers. Ex. 40.7 L has 3 sf 56003 has 5 sf2. Dont count zeros before nonzero numbers.Ex. 0.000078 g has 2 sf 000023.85 has 4 sf

Zeros at the end of a number after the decimal are significant.Ex. 83.00 km has 4 sf 0.005520 cm has 4 sfDo not count zeros at the end of a whole number Ex. 2000m has 1 sfRounding off NumbersUse math rules if number to be considered is 5 or greater, round up if number to be considered is less than 5, round down.

Ex. Round this number to 5 sf, then to 3 sf, and finally to 1 sf. 3.515014

Addition and Subtraction of S.F.Keep the fewest # of decimal places that is in any of the entries.

Ex. 28.0 cm + 23.538 cm + 25.68 cm = 77.218 cmRound answer to one decimal place because the 1st entry has only one decimal.Multiplication and Division of S.F.Keep the fewest # of significant figures that is in any of the entries.

Ex.3.20cm x 3.651cm x 2.2cm = 25.70304 cm3Round the answer to two s.f. because the last entry has the fewest s.f.

Prac. 49Scientific NotationScientific notation-expressing a number in this form: _._ _ _ x 10xWhen the number is larger than one, the exponent is positive.When the number is smaller than one, the exponent is negative.Ex.1 392 000 km =0.000 000 028 g/cm3 = Chemical Names and FormulasChapter 7Chemical FormulasChemical Formulas number of each kind if atomEx. C8H18 , Al2(SO4)3

Memorize the charges of common monatomic ions using periodic table

Grp 1 elements +1 chargeGrp 2 +2 chargeGrp 13 +3 chargeGrp 14 +2 or +4 chargeGrp 15 -3 chargeGrp 16 -2 chargeGrp 17 -1 chargeGrp 18 0 chargeGrp 3 to Grp 12 Transition Metals have varying positive charge.

These 3 ions do not vary in charge:Ag+1, Cd+2, Zn+2

H+1 OR H-1Naming Monatomic IonsPositive Ions use element name and add word ion Ex. K+1 potassium ion

Ions with varying positive charge have a roman number after the name to indicate the charge of the ionEx. Fe+2 iron(II) ion OR Fe+3 iron(III) ion Pb+2 lead(II) ion OR Pb+4 lead(IV) ionNegative IonsNegative Ions use root name (drop last syllable) + -ide ion

Examples:F-1 fluoride ionNote: H-1 hydride ion O-2 oxide ionBinary CmpdsBinary Cmpds cmpds with only two different elementsWriting Ionic CmpdsSteps:Write symbol and charge of positive ions first.Write symbol and charge of negative ion next.Use subscripts if more than one ion is needed to make the total charge of the cmpd zero.Polyatomic CmpdsCmpds with polyatomic ions use parentheses when more than one set of polyatomic ion is needed.

ExamplesTin(IV) sulfateCalcium chlorateMagnesium phosphate

Prac p211Naming Ionic CmpdsName cation, roman numeral, name anion (if needed)

Examples: Name LiHNa2SO4MgCl2CuCl2Al2(SO4)3Binary Molecular Cmpd.Naming Binary Molecular Cmpd only 2 elements in formulaMemorize the Greek prefixes for one to ten p212

Mono, di, tri, tetra, penta, hexa, hepta, octa, nona, deca 1 2 3 4 5 6 7 8 9 10Molecular Cmpds.Less electronegative element (more metallic first), and prefix to element to show number of atoms. Omit mono- for the first element.Add prefix to root name of second element and add ide ending.Covalent Network CmpdsAtoms covalently bonded to its neighbors in a 3D network

Ex. SiC IllustrateAcidsAcid compounds with the hydrogen ion, H+1 , first in the formula

Hydrogen Anion Acid Name -ate -ic acid -ite -ous acid -ide hydro- -ic acid

Ex. Hydrogen sulfate ________ hydrogen sulfite ________ hydrogen sulfide ________(note: ur added in for S and added in for P)

Section Review p215Using Chemical FormulasFormula mass sum of all masses of atoms in formula

Ex: formula mass of:a. Feb. O2c. H2Od. C12H22O11

Practice p222Molar MassMolar Mass mass in grams of one mole of a substance

Ex. Determine the molar mass of:a. Feb. O2c. H2Od. C12H22O11

Practice p223Formula Mass Vs. Molar MassNote: The only difference between formula mass and molar mass is the unit of amu and grams.Chemical Equations and ReactionsChapter 8Chemical RxnChemical rxn is the process where one or more substances are changed into one or more different substances. The atoms are separated, combined, or rearranged, not created or destroyed.

Chemical equation: chem. rxn represented by formulas and symbols.

Writing word eqn and formula eqn description of rxn:

When solid sodium oxide is added to water at room temp, it forms sodium hydroxide dissolved in water.

Sodium oxide + water sodium hydroxide Note: word eqn doesnt indicate state

Na2O (s) + H2O (l) NaOH (aq) Note: state included, but not balanced yet

Prac. p248Balancing RxnsCoefficients are used before the formula to indicate multiple sets of substance.Ex. 2MgOSignificance of Balanced Chemical Equation:Ex. Mg + O 2MgO 1 atom Mg 1 molecule O2 2 formula units MgO 1 mole Mg 1 mole O2 2 moles MgOWriting Balanced Chemical Equations RulesWrite correct formulas.Balance atoms that appear once on each side of eqn first.Balance polyatomic ion sets.Count atoms to check eqn is balanced.

Other Helpful Hints to be an Expert at Balancing Chem EqnsIf odd number of atoms on one side of eqn and even number on other side, DOUBLE only the odd number.If water is a product and hydrogen and hydroxide show as reactants, then rewrite water as H-OH.Expertise comes only from practice, practice, practice5 types of RxnsSynthesis rxn, or composition rxn, or combination rxnDecomposition rxn, or analysis rxnSingle replacement rxn, or displacement rxnDouble Replacement rxnCombustion rxnSynthesis RxnSynthesis rxn two or more substances combine to form a new compd.A + X AX*Be sure to look at charges when forming cmpds.

Examples:Mg + O2 Na + Cl2 aluminum + fluorine CaO + H2O

Be on the lookout for:*Metal oxides react with water to produce metal hydroxidesDecomposition RxnDecomposition Rxn a single cmpd breaks down to two or more simpler subst.AX A + XElectrolysis (electrical current) can be used for decomposition as in the case of water.

Hints for Decomposition RxnsBinary cmpds decompose into their respective elements.H2O

Metal carbonates decompose into metal oxides plus carbon dioxideAl2(CO3)3

Metal hydroxides decompose into metal oxides plus waterMg(OH)2

Metal chlorates decompose into metal chlorides plus oxygen gas.NaClO3 Carbonic acid is unstable and decomposes to carbon dioxide and water almost immediately upon formation.

Single Replacement RxnsSingle Replacement Rxns one element replaces a similar element in a compd.A + BX AX + B ORY + BX BY + X ORA + BX NR (no reaction)

Must check Activity Series of Elements if replacement will or will not take place. Check p.266 or handout. An element will replace any element below it.HINT: Replace H2O with H-OH Double Replacement RxnsDouble Replacement Rxns ions of two compds exchange to form two new compds. Must be both aqueous solutions. This reaction only takes place if1. a precipitate is formed 2. a gas forms 3. water formsDR Reactions AX + BY AY + BX

Examples:Al2O3 + NaF KI + Pb(NO3)2 FeS + HCl HCl + NaOH NaNO3 + CaSO4

Combustion RxnsCombustion rxns a substance combines with oxygen, releasing a large amount of energy (light and heat)X + O2 XO

Ex.H2 + O2 C3H8 + O2 Mole equivalents

MOLEPART ICLESGRAMSAvogadros NumberMolar Mass89Ask students to turn to their table partner and come up with a conclusion to describe the relationships depicted in this slide. Have some groups share their answers verbally with the entire class. Then, summarize to affirm main ideas. Molar MassThe mass in grams of 1 mole of the compound

C10 H6 O3 10 C = 10 X 12.011g = 120.11 6 H = 6 X 1.008g = 6.048 3 O = 3 X 15.999g = 48.997

TOTAL = *175.16 grams

*Remember the significant figures rules.

90When calculating molar mass, it is recommended to have students carry the atomic mass as written on the STAAR Chemistry Reference materials to their calculations. Since the least number of decimal places with this addition problem is 2, then the answer would be written with two as the STAAR Reference Materials inform.Molar MassThe mass in grams of 1 mole of the compound calcium carbonate

CaCO3 Ca 1 X 40.078 grams = 40.078 grams C 1 X 12.011 grams = 12.011 grams O 3 X 15.999 grams = 47.997 grams

TOTAL = *100.086 grams

*Remember the significant figures rules.

9140.078 g + 12.0111 g + 47.997 g = 100.086 g---This sum written is 100.086 g since the least number of decimal places is 3. (STAAR Chemistry Reference Materials) Stoichiometric Calculations The PlanWrite the chemical equation.Balance the chemical equation.*Follow steps to dimensional analysis:Start with what is given.Set up a series of equivalent measures.End with your goal.Solve the problem by cancelling units.Record the appropriate answer with units.

92For this type of problem, steps #1 and #2 do not apply since the calculation involves the same element or compound. The balanced equation steps (#1 and #2) are part of the plan if you are taking a measurement from one element or compound and determining the answer for another reactant or product. For this calculation, we are staying with calcium carbonate for our unknown, goal, so steps #1 and #2 are not applicable. Start with step #3 for this calculation.Chemical EquationsRecipe for a chemical reactionRelative number of reactants and productsCoefficients represent the relative numbers.

CH4 + 2O2 CO2 + 2H2O93Bridge the connection from the models to the chemical formulas. Students did study equations in Grade 8 with this SE- recognize whether a chemical equation containing coefficients is balanced or not and how that relates to the law of conservation of mass. These slides serve as a review to make the relevant connections to using the balanced equation in stoichiometry. You could have students use the molecular model sets to build this reaction and reinforce the meaning of the coefficients and visualize the process and make connections to the model and this illustration. Law of Conservation of Matter: BalancingChemical EquationsAtoms are conserved in a chemical reaction.Coefficients are manipulated to balance chemical reactions and create equivalent measures. Identities cannot be changed.

_C2H5OH (l) + _O2 (g) _CO2 (g) + _H2O (g)94You many want to have students build this model before they manipulate the coefficients to help students visualize the concept of matter. Point out the way the number of each colored ball is the same on both sides of the arrow to demonstrate law of conservation of matter.BalancingChemical Equations

C2H5OH (l) + O2 (g) CO2 (g) + H2O (g)Count Atoms:Carbon 2Carbon 1Hydrogen 6Hydrogen 2Oxygen 3Oxygen 395BalancingChemical Equations

C2H5OH (l) + O2 (g) CO2 (g) + H2O (g)

C2H5OH (l) + 3O2 (g) 2CO2 (g) + 3H2O (g)96Chemical Equations as EquivalentsCoefficients from a balanced equation represent the number of theoretical mole equivalents and can be used in stoichiometric calculations. 97Stoichiometric Calculations The PlanLiOH + CO2 (g) Li2CO3 + H2O (g)

2. Balance the chemical equation.1. Write the chemical equation.2 LiOH + CO2 (g) Li2CO3 + H2O (g)98Stoichiometric Calculations The Plan2 LiOH + CO2 (g) Li2CO3 (g) + H2O (g) 48.0 g LiOH X 1 mole LiOH X 1 mole CO2 X 44.009g CO2 = 1 23.948 g LiOH 2 mole LiOH 1 mole CO2 Follow steps to dimensional analysis:

99Stoichiometric Calculations The AnswerWhen 48.0 grams of lithium hydroxide are available for use in a reaction, 44.1 grams of carbon dioxide can be processed by the reaction.

*Remember the significant figures.100