Chemistry Practice Problems Part 2

lsotope Notation Name --------- Any given element can have more than one isotope. То distinguish between the .different isotopes of an atom, the element is named with its mass num.ber, for example lithium-7. Remember that the mass nwnber is the number of protons and neutrons. When symbols are used to represent an isotope the mass number is written next to the symbol on the top left. Тhе atomic number is written on the bottom left. Recall that the atomic number is the number of protons. EXAМPLES Mass number ---._ А Atomic number ---._ Z Lithium-7 Х 7 3 L1• 3 protons 4 neutrons Answer the following questions about atoms. З. fro fО n 5 Тhе particle(s) found inside the nucleus are called: proton� anot_, neнfrons. Тhе number of protons and neutrons combined is called the h')tj�S nит Ье r . 4. In large atoms the number of protons is 5. Тhе number of protons is also called the 1. 2. Тhе identity of an atom is deteпnined Ьу the number of J ess than the number of neutrons. 6. wtvmiс. пит Ье г. Isotopes have the same number of pro -Ьиы , but d.ifferent numbers of neи.fr-ons. 7. Тhе number of protons found in а sulfur atom is 8. Тhе number of neutrons found in an aluminum.-27 atom is 9. Тhе number of electrons found in а zinc atom is 10. What is the name of the element with 82 protons? /(р 3 (J i Lf / ett С1 Give the syпibols for the nuclides described Ьу the following particles. lnclude the atomic number and the mass number. ��1 20 protons, 20 neutrons 11. 15. 92 protons, 145 neutrons tl'J... U 12. 8 protons, 10 neutrons 16. 22 protons, 23 neutrons 13. 82 protons, 125 neutrons 1 7. 18 protons, 22 neutrons 14. 80 protons, 119 neutrons 18. 25 protons, 32 neutrons 111.\, 1 �о\"1';) б7 d,>)'\f\ Determine the number of protons and neutrons from the follow.ing symbols. � r 19• IOB 20. 1 sN / 21. 19S з4 е ЗЦ () 22. s 19Sn 150 !i/J р � ti ц 5/V ,S-r) и р N 23. 6 16 6S Dy 24. sбFe 25. шsm 26. 195 Pt (р{, р 4'1/\J .еь Р 30 fV ";2 f �q tJ "7 Ь' р 117 .tJ 2 7. 126Те 28. зsс1 "29. 101 30. 5). f '7ЧrJ Ag 9 3? 41 • \( р l�N i.п Р (о о fJ с,з Nb �\ 1=1e-ctroп-eonftgптation Name --------- An electron configuration is simply а list of the orЬitals that contain electrons for а given element. Тhе orЬital designation is followed Ьу а superscript number that tells how many electrons are found in • :, ' ; ;. 2 •· 12)._, ·в •. • .. • • . , · that orь1·ta1. The following designation represents an atom with electrons ,,•. '_;··· •··,'.Et" ;-"· ·1-� 2.#.--.гр зs,· ,. ., • .. · · found in the ls, the 2s, the 2р, and the Зs orЬitals. There are а total of 11 •;·.i. -·�:;,.;·�<.и,..� ;:; •;.t ;.; ;.: • electrons in the atom. This represents the element sodium. .. Qфit_atn�e : :NщnЬ�_q(eJectФn� . . . . . .. : .. ' ... Тhе orЬitals of an atom fill in а specific sequence. The pattem fits very nicely with various regions of the periodic tаЫе. Тhе tаЫе is been sectioned into Ыocks which are labeled: s Ыосk, р Ыосk, d Ыосk, andfЫосk. Тhе rows of each Ыосk are labeled as well. Using this shortcut, electron configurations can Ье determined easily. Тhе element manganese is the fifth element in the 3d row. Тhе orЬitals before the 3d orЬital are а11 filled so it has full ls, 2s, 2р, Зs, Зр, and 4s orЬitals. Since manganese is the fifth element in the 3d row we designate the 3d orЬital with 5 electrons. Electron configurat:ions can Ье abbreviated Ьу writing the element symbol for the previous nоЫе . , .. - .. .. ., , . .. - .., . .. . . .. ... - ., , ..... . ... , ... ............ . gas in brackets, followed Ьу the remaining electrons. For example, rather than writing а11 of the :$Ь.;.1!f.2.bp���3P64iici?4p�5�4:d1 �5_p3.;�';:�b; .-·; ..: · .: � .: � · ;� . �-;: :, ; ,,.:.: · _; •�р�•-··: �, .-:.. ; .: : :.;. .:. :. • ; -� ·: electrons in antimony (element 51), the first 36 кr electrons are represented Ьу [Кr]. The remaining ;� ;;.�&{�;f electrons are notated using orЬital names and . -� : .: :.:· :. : ;;_� [�� ·p.s. 1Р. "'Р.Р .::: ....: _ : ; . � .:· �gw'atjo�-. •. ��.-. ;. �-;· • � ·.: : ·-� t ...·t��:: , :-:.-·; : 1·:: � t ·c°i'.� :···!., � -::·., ;'::- ;·:.� .• ,�.-�: -r-� • ; superscript numbers. : R, t.{ iv-ed а.,И 'e,Ve,,v) ptolal�s-. J�;1·:; ;_ .;:,·.;-;:;; ·�:; �;��_;: ; co бi Write the name and symbol for the atoms with the following electron configurations. 5е 1. 1s22s22p6 Зs2Зp64s2Зd104p4 2. 1?2s22p6з?зp64s2Зd104p65s24d105p66s1 C.s � \-\ 3. ls22s22p6 Зs2Зp64s2 3d104p65s24d7 4. 5. 6. 1?2s22р6зs2Зр 1 А1 2 -'В k [Rn]7s 5/ fЬ [Хе] 6s24/ 45d10 6p2 Write complete electron configurations for the following substances. 7. nitrogen 8. magnesium / r/ 2/ Zr 1-, Jsz, 9. nioЬium i 2 1o z 10. nickel /s 2s z f 3./ 3р' �s 3d 11. tin 12. cblorine / s Z Z s i 2 f � 55 � 3 р 'cJ- Write abbreviated electron configurations for the following elements. 13. arsenic 14. thulium 19. sulfur 1)-е,] �s 2 4t 13 15. ruЬidium 16. einsteinium [Р,1'\'1 l 51.. 5 •f 11 17. plat:inum 18. molybdenum L �Г l 5 5 2 ч� � 20. zirconium [K r 1 5s 'l 1td 21. argon 22. iron [/tr J � � 2. 3d lP 23. polonium 24. bohrium Lr'Zn l 7 5 2 f; t 2 14 C,0i 5' 5' Naming lonic Compounds Name ---------- An ionic cornpound is а comЬination of oppositely charged ions. Ionic compounds generally contain а metal bonded to а non-metal (or non-metals). When naming ionic compounds we simply name the cation (the positive ion) then the anion (the negative ion). The cations genera11y retain the name of the element, so Na+ is named sodium. The monatomic anions are foпned when а non-metal gains an electron and these ions have an -ide ending, so s2- is named sulfide. There are а group of polyatornic ions as well that -have their own unique names. А list of these appears below. Some metals сап form more than one positive ion. Copper for example forms Cu 1+ and Cu2+ ion. These ions are named using Rщnan numerals: copper (1) and copper (П) respectively. Most metals that form more than one type of cation are found in the transition metal family or below the non-metals in thep-Ыock. Rules for narning Molecular Compounds 1. Name the positive ion. Most cations have the same пате as their elements. 2. Name the negative ion. Monatomic anions have ап -ide ending. Polyatomic anions names' must Ье memorized. 3. lf the positive ion is а transition metal or located оп the right side of the tаЫе it may have more than one charge. In this case use Roman numerals to designate the charge. , � � i f. � t 1 t 1 ii ll fJъ\lfJ*' i# ·\. Common Polvatomic lons Arnmonium NН/1Hydroxide он 1 Cyanide CN -1 N0з 1-Nitrate Chlorate СЮ3 1 С2НзО2 Acetate SО42Sulfate СОз2Carbonate Phosphate Ро/HC03 Bicarbonate HS04 1Bisulfate 1 i�i;�fi1;1: :;::::.: ��� •.!f�\i:i:�};�:-1{·�- • :i:l�!}i�й2iii�,�;:i\;; i?,t\::t�\1};fJ;,;J,11.tii;i)f;!?iri�:'i:1.fiйf1,:ЭEi��;;}t?Шtil?__. ,_ , Write the names for the following ionic compounds. 1. 2. 3. М зN2 4. Са(ОН )2 5. Ва(NОз)2 6. CuCI2 7. РЬО 8. ZnF2 9. NаС2НзО2 10. SrCOз 11. CrSO4 Chrd 12. NазРО4 So d.-,· t.t"" Name с/ r: fe 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. Formula СаВr2 Ni(CN)2 Аl(NОз)з Sn(OH)2 Hgl2 Fe2(SO4)з Са(С2НзО2)2 TiClз КСIОз ZпСОз NаНСОз Co(HSO4) 2 Narne С"/ G i и. т J!..j,1,,., t'd е ,f,'c..ke-i {11) Lt1<:.n ;Ае lttLA.tл,·1iu,m hifra,,fe ·1/п (/l)/-k,,,drp�;de f1tJrl,И1ru {11 J ..Tb"4,'de .J-ron (111).Sцtfд__fe.. 1 (4 lc ;1.011 А с ei ""-+е f� fA.Z/u.rn С h/ О ГI{. f е, 2/iu,,. CarbtJnи f� Sо d..-t'�n, JJ, 't!аr 1, опti,,f-e. lobA-/f {Jlj g;<>l-f.lfii fe Wtit1ng Formulas: lonic Compounas Name --------- Ionic compounds are composed of а positive ion and а negative ion bonded to�ether in а specific proportion. For example, magnesium chloride is made of one magnesium ion (Mg +) and two chlqride ions (С1 1-). These two ions are combined in а ratio that creates а neutral compound (MgCl2). The 2+ charge оп the magnesium ion is balanced Ьу the two negative charges from the chloride ions. All ionic compounds follow this rule: the charge from the positive ions must Ье equal to the charge from the negative ions. In а compound of aluminum ion (AJ 3+) and nitrate ion (NO3 l there must Ье three nitrate ions. So, the forrnula for this compound is Al(NO3)3. Recall that nitrate is а polyatomic ion, so this comblnation of atorns remains intact when writing а chemical fonnula. Also notice that the proper way to designate more than one polyatomic ion involves the use of parenthesis. An easy technique for creating а neutral comЬination of two charged ions is called the criss-cross technique. When writing а foпnula for an ionic compound the charges from each ion are simply switched to become the subscript values written to designate the number of atoms present in а compound. See the example below. Comrnon Polvatomic Ions 1 он 1 NН4+ CN 1NОз1- The Criss-Cross Technique сюз 1- Write the chemical foпnula for calcium phosphide. 1 С2НзО2 2 S04 - со/­ Ро/нс оз1- нsо4 1- Ammonium Hydroxide Cyanide Nitrate Chlorate Acetate Sulfate Carbonate Phosphate Bicarbonate Bisulfate Write the chemical formulas for the following ionic compounds. Remember all ionic compounds must Ье neutral. Formula Formula Name Potassium oxide Ammonium chloride 15. Calcium nitrate 16. 5. K1D лl"z5 NЩ С:/ Са (,JOl),. Fe f3r1 Iron (II) bromide 17. 6. Сr(оН)з Chromium (ПI) hydroxide 18. 'SrSOч Copper (II) sulfate 19. Aluminum iodide 20. A1·ts Fe зСfDч)� Ammonium carbonate 21. L-ц --., Nz. Lithium bisulfate 22. Manganese (III) oxide 23. 1. 2. 3. 4. Си�Оч 8. Al.1; 9. Nffч1. G03 7. 10. li нsо 4 11. f1n 2 0 3. 12. 5"(C10j)� Sodium sulfide Tin (IV) chlorate 13. f1q(IJCOз) -z. 14. 7.nOH Name Magnesium Ьicarbonate Zinc hydroxide k:t.PDч Potassium phosphate н� t 1 Mercury (ll) chloride АJ{Л/03) 3 ;). fbO:J. Сц :)_ t о� 24. NМ/ CJ Н-3 О;;.. Aluminum acetate Strontium sulfate Silver sulfide Iron (II) phosphate Calcium nitride Lead (IV) oxide Copper (l) carbonate Ammonium acetate Naming Molecular Compounds Name ----------- А molecular compound is а group of atoms held together Ьу а covalei:it bond. Compounds made entirely of non-meta]s are generally molecular compounds. Carbon tetrachloride, СС]4, is an example of а mo]ecular compoнnd. When naming these compounds prefixes are used to denote how many of each atom is bonded in the compound. However, the prefix топа- is not used with the first element in the compound, even if there is only one element. The ending of the second element in the compound is a]ways changed to -ide, in the same way the ending is changed for monatomic anions. Naming Prefixes Rules for naming Molecular Compounds 1 2 3 4 1. Name the first element using the element' s full name. 2. Name the second e]ement using the -ide ending. 3. Use prefixes to tel1 how тапу of each e]ement is present. (do not use the prefix топа- on the first element). monoditri- 5 6 7 8 tetrapentahexaheptaocta- 10 deca- 9 попа- Fill in the following tаЫе with the missing information. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Formula SO2 N2O4 Р4О10 С57NO2 N2Cl4 S2Cl2 P2Ss Name 5111 fuy o;o:x.de Sulfur trioxide Те.� м'+rо 10•'o;tiJ\ � D{n,� � e,\,i ,, (1 Xenon difluoride f);sи\&v Oie,.i,,.\i,i;c;\ � Iodine trichloride \:); k V $wl . е., 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. Formula SFб ()lj s Name Sчltt-tr v,d е.. Tetraphosphorus hexasulfide 5-ele,nit.\.w-> 10i'o�d,-G Ammonia Boron trichloride оу,,'Д.,� (_С) CIFз J.C\ СН4 Carbon dioxide Carbon monoxide С\--. \tii', n-e tr,' �!Al'V' i t:t е... Iodine monochloride r ,'ttr.. • -L m--e,,'+¼� е D1mensional AnalysisRev1ew Name --------- There are а variety of units that can Ье used when measuring.For example, the length of an object can Ье measured in miШmeters, centimeters, meters, and even inches. А measurement made in inches can Ье converted to other units, such as centimeters using а conversion factor. А conversion factor is а ratio of two equivalent values expressed with different units. Conversion Factors 1L=l000mL 1m=100cm 1 gal=3.785 L 1km=0.6214 mi 1 yek= 18mem 1km=1000m 1mm=l000µm 1in=2.5 4cm 1kg =2.2 0lb 1mem=180tezl То solve conversion proЫems we use а strategy known as dimensional analysis. Тhis technique focuses on canceling units Ьу placing them on the top and bottom of the fractions used to set up а proЫem. For example, when converting 18 inches to centimeters we place the inches on the bottom of the conversion factor so that they cancel with the inches in the 'given'. 18щх 2.54cm =45.72cm 1 l'щ :Example •••• • • • ... • .. .... .. . ... . . •• • ' •f � z\3l. P\f-;) (�s;�ti�) 8. Convert the m.easurement 3 2 5 m.i to km. �. �1 )( 3��� х 0.11, ;1.� =-f G�З jё,;}(; .s��fiy 9. Convert 180cm to in. .--/ )Ь � х \ iм :- \ 7-1 -i;) (;. J �� --.. Z. �� C.rn 10. Convert 42 mem to yek . Ч'). т�� х I y-e.\t. �/_;t._3_Ч_t-�J (�.r·,� 1 S' �tr}, J"М l-,y t,·v Chemistry Calculat,on ev1ew Name --------- The first step in performing а stoichiometric calculation is to write а balanced equation. Recall that balancing an equation involves placing coefficients before each of the reactants and products in order to ensure that the number of each type of atom is the same before and after the reaction. �Al + l_Cl2 - �AlClз Ех. Another important aspect to doing а stoichiometric calculation is finding the molar mass of an element or compound using the periodic tаЫе. The molar mass of iron (III) nitrate is shown below. А1С1з �,1 26.98 + 3(35.45) = 133.33 g/mol Finally, the aЬility to convert units using dimensional analysis is an important skill in performing stoichiometric caJculations. In this technique conversion factors are placed next to values in а manner that allows units to Ье cancelled. An example of а mole conversion is shown below. 6.3.g.dl3 1 mol AICl3 •х = 0.047 mol AlCl3 _ �3 133.33 V"''-1 1 Balance the following equations. 1. _Mg(OH)2 + 2. 2 1:.._к + _Br НС1 -+ _MgCl2 + �Н2О -+ -1.._квr 2 3. _Р4О10 + G:.н2О -+ 4. ').. SОз -+ J. 4 НзРО4 SO2 + _02 5. (р Na + _Fe203 -+ 6. ;;2 Na + ;). Н2О -+ 2 3 Na20 + Z. Fe NaOH + _Н2 Find the molar mass of each of the following compounds. 10. SОз 7. Мg(ОН)2 �l• 3J. g/l'Y"\71 8. КВr / \ q ,00 9. Н3РО4 go , (J 5/ у,.л.,,.. 1 ьr 1"-9 1 J5'q,11/f\,\,,Q1 {р(, q7, t?t) �/f"\,\J I q8' Convert the following measurements. Show all work, including units that cancel. (А.¼�� 18.2g - ? mol 18.1�(-'-��\•\ � v- 14. l��J\ 8.5 х 10 4 molecules NO2 -+ 2 � ( (р х. \ 0 Z!.,\ес-�'•1\J� )l _!!.2), 15. 82.6 L of neon at SТР -+ rnol ) © John Erickson, 2005 ( �\�� 1iьq�\\ Ne .&.{ 16. 4.I4gofNa,O - mol 17. 9.3 mol SO3 -+ liters в-s� ( -Z.1::1i) � \2 of' Lj \V,,W 18. 1.4 х 1024 atoms ofK-+ mol�. / 3 rм \ К"\ z,� _\. (' \-\№\ \.t\X.\\) ц-Wvnt z. / • / ChemCalcReview �. Оµ \D �) б.,'10� Mole Conversions Name ---------- lt is important to Ье аЫе to convert units from and into units of moles. The mole is а unit for count, as is the dozen. А dozen is 12 items, but а mole is 602 ООО ООО ООО ООО ООО ООО ООО, or 6.02 х 10 23 particles. Using the periodic tаЫе we сап find the molar mass, or the mass of а mole of а substance. The molar volume is the volume of а mole of substance. Mole Converslon Strategy All gases have the same. molar volume when measured at standard temperature and pressure (STP) : 22.4 Umol. Mass These values allow the conversion of grams, liters, or ss g( / mo l __ <&_r a_m _sJ__ � particles into moles. � --... .,... _ _ _ Volume of gas (lit e sr ) Particles -- 22.4 Umol ( ➔ Amount (moles) / (atoms, molecules, /42 х I01J panicles/ mol fornшla units) бУ) Answer the following questions. l. А sample of neon has а volume of 75.8 L at STP. How many moles are present? 7. Convert 7 .8 liters of carbon tetrafluoride CF4 to grams. 2. What is the mass in grams of а 8.4 mole sample of iron? 8. А gold coin contains 3.47 х 10 23 gold atoms. What is the mass of the coin in grams? 3. Convert 0.45 g of sodium hydroxide, NaOH to moles. 9. What is the volume in liters of 7500 g of helium atoms. Assume STP conditions. 4. How many molecules are present in а sample of carbon dioxide, СО2 with а mass of 168.2 g? 10. А teaspoon of salt, NaCI has а mass of about 5.0 g. How many formula units are in а teaspoon of salt? 11. What is the mass of 500 trillion (5.0 х 1 О14) 5. How many mo]es of potassium nitrate, КNО3 are present in а sample with а mass of 85.2 g. 6. What is the mass in grams of 0.94 moles of sodium Ьicarbonate, NaHCO3? molecules of water? 12. One component of smog is nitrogen monoxide, NO. А car produces about 8 g of this gas per day. What is the volume at STP? Stoichiometry ProЫems Name ----------- With а balanced equation it is possiЫe to calculate the amount of expected product or reactant for а reaction. The products are the substances formed in а chemical reaction and these are found оп the right side of the reaction arrow. The reactants are the substances required in а Stoichiometry Strategy chemical reaction and these Mass МJlss grams grams are written on the left side of molar mass (g/ ol) mass (g/mol) / � . the arrow. Using the technique mole mole ratio of unit cancellation and the 22.4Umol Volume of gas Volume of gas 22. 4Umol Amount В atSTP strategy outlined to the left, atSTP � � AmountA moles moles liters liters given the mass, volume, or number of particles of а 21 particleMmol 6.02 х 1023 pa�ol 6.О?/4 А Paгticles Paгticles substance, it is possiЫe to tmn�·. 1110/ec11/es tom�·. 1110/11c11/11s, / " determine the mass, volume, Jor11111/a 1111its Ja11nula 1111its KNOWN UNKNOWN .. or particles of another. . ·:;:wha ):\J{::.i(+:-· fб':}i:duce'.25:I;l�j�i�8ir.:·c,f }:: ·:]:ti\clro' : i.;-�::1:�''e"�:\n.'·/ ia�ts•::ia�fi"ST.�1:ii·P[:SJ.ini:}:tne�i'teact i :�;:{:ioriЪelov.i?) �/:1:t;I�::::.: :.{_.::·:. - -;,� . ·,'. . <>, ·- .:':·.: ·:,_· :;�: ::_ ·: �:-;,Ш.:].:i;:.i:iI1s're':�:;:: :•�:·;шiеiНб'.' ;�t��;t· ma·_f��ss:Jьf{.!'alumiiIO'in'· ·; ° \� ч�;�1:�1!�tiiii !�l�;11i{ifll�i!i;fl!III�i:J�1�,t�i; i:i�i�{i.,:,;i: й;\_fii�{l!I!lI� JiJ�ifi �flII�f�ii�1i!�'f@�;!f�:t,i ��b · ·, ••_ dёvelop'a 'strategy•·:,....·-,-·'·•·.•·'··; 'f','-•:, •,;•, ',: .. ·- ··! •. liters•H' 4·molёs H·.Ц:tnolёs·:A:L:.,,2f··grairis:AJ·,.· · •• ,.·. ·::,·:-'·' ••. ,,,· � · : · · . ·. . ::·:•· . • :_,.•_ .. >.. - :·· ·· _. fill i1i'con'versiorl'faetors"-•:;;-:,�.:-�<,,:-:;,;;,:.?".��-.:;.�·..,/ ;.:.. 2518 �·'; ::l:m�:-:.,,,2 rriOi¼l-:':·,.20:98:g:д].:�:- :.·-.,;,::'(..;., Balance the following equations. Solve the stoichiometric proЫems. t\-eqц ·,v-e.J... \- 5 6'() �6 'oack - l. How many molecules of oxygen are required to react with 174 g of carbon monoxide? _СО+_О2 - _СО2 6. If there are 6.2х 10 22 molecules of calcium carblde, СаС2 , what mass of acetylene (С2 Н2 ) сап Ье formed? _СаС2 +_Н2 О - _Са(ОН) 2 +_С 2Н2 2. How many liters of oxygen at STP are required for the combustion of 1.4 g of magnesium? _Mg+_O2 - _MgO 7. What mass of sodium iodide (NaI) wil\ react with 7.82 grams of chlorine? _NaI+_Cl2 - __:_ NaCI +_12 3. What mass of hydrogen peroxide must decompose to produce 48.64 g of water? _Н2 О2 - _О 2+_Н2О 8. If 8.2 L of hydrogen gas at STP are produced in this reaction, how many atoms of sodium react? _Na+_H2O - _ NaOH+_H2 4. How many liters of oxygen at STP are needed to react with 5.2х10 22 molecules of hydrogen sulfide? _H2S+_O2 - _SO 2+_H2O 9. What volume of nitrogen gas at STP is produced when 68.2 g of trinitrotoluene, C7 H5(NO2)3 reacts? _C1Hs(NO 2)з - _С+_CO+_H2 + _N2 5. What mass of chlorine gas is necessary to synthesize 258 L of hydrogen chloride at STP? HCl _H2+_Cl2 - 10. What mass of carbon dioxide is produced when 6.2 moles of propane, С3Н8 is burned in oxygen? _СзНs+_О2 - _СО 2 +_Н2О