CHE 546
Chemical Engineering Calculations !! "roblems with Answers
Submitted By: De Belen, Joewee D. Submitted To: Engr.. Lorraine A. Carrillo Engr
CHE CALCULATIONS 1 CONCEPTUAL QUESTIONS 1. Which of the following is not a raw material used for the manufacture of ordinary glass? A. Iron oxide B. Soda ash C. Limestone . Silica 2. !"#$C%s S.&.#. corres'onds to $. ( atm a)solute 'ressure and (5.5 *C B. +6, mm Hg gage 'ressure and (5.5 *C
C. 760 torr pressure and 0 °C . (,(.-5 /#a gage 'ressure and , *C
3. Which of the following ratios defines the recycle ratio in a chemical 'rocess? $. 0ross feed stream1recycle feed stream C. 2ecycle stream1gross feed stream B. Recycle stream/res! eed stream . 3one of the a)oe ". &he tem'erature at which real gases o)ey the ideal gas law oer a wide range of 'ressure is called tem'erature. C. Critical $. 2educed B. Boyle . !nersion #. &he reerse 'rocess of fractional crystalliation is called $. Stri''ing C. ifferential istillation B. $eac!in% . $)sor'tion 6. $ chemical 'rocess is said to occur under unsteady state if the $. inentory changes do not ta/e 'lace B. ratio of streams entering1leaing are inde'endent of time C. lo& rates and composition 'ot! are time dependent . none of the a)oe 7. 7ethane is mi8ed with stoichiometric 'ro'ortion of o8ygen and com'letely com)usted. &he num)er of additional s'ecifications re9uired to determine the 'roduct flow rate and com'osition is C. 2 $. , B. ( . (. Sometimes in a chemical 'rocess: 'art of the outlet stream is re;ected as waste in order to /ee' the im'urity leel in the systems within limits. &his 'henomenon is termed as $. 2ecycling C. By<'assing B. )ur%in% . 2ecirculation *. $ =limiting reactant= is the one: which decides the in the chemical reaction. $. e9uili)rium constant C. rate constant B. con+ersion . none of these 10. $ )y<'ass stream in a chemical 'rocess is useful: )ecause it A. acilitates 'etter control o t!e process B. im'roes the conersion C. increases the yield of the 'roduct . none of the a)oe 11. &he 'hysical se'aration of com'onents in a misci)le mi8ture )y simultaneous ea'oration and condensation is. $. a)sor'tion C. e8traction ,. distillation B. drying
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CHE CALCULATIONS 1 12. !n 'a'er industry: 'a'er is dried in $. tunnel dryer B. coneyor dryer
C. !eated cylinder dryer . festoon dryer
13. &he 'ercentage ratio of the e8cess to the amount that is theoretically re9uired )y the stoichiometric e9uation for com)ination with the limiting reactant is called $. > com'letion C. degree of conersion ,. - excess B. > yield 1". Starting raw material for the manufacture of alum is B. %ypsum $. alumina C. )au8ite . ammonium )icar)onate 1#. Styrene<)utadiene
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CHE CALCULATIONS 1 23. &he 'ortion of water in the wet solid that cannot )e remoed )y the air in its contact is called $ free moisture B final moisture C euili'rium moisture content critical free moisture 2". $ se'aration 'rocess wherein a li9uid solent is used to dissole a solu)le solid from an insolu)le solid $ solent e8traction B a)sor'tion C leac!in% adsor'tion 2#. !t is a ty'e of 'hysical o'eration )y which a desired ste' in an industrial 'rocess is controlled or conducted. $. unit 'rocess B. chemical 'rocess C. unit operation . heating 26. $n a''aratus in which 'articles settle in a li9uid )y graitational or centrifugal force and are remoed as a concentrated slurry. C. t!ic4ener $. classifier B. elutriator . agitator 27. Which of the following does not affect the amount of dissoled o8ygen in water? $. heat C. chlorides ,. dissol+ed minerals B. )io
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CHE CALCULATIONS 1 3". #ic/ out the wrong statement a)out the recycle stream in a 'rocess. $. 2ecycling in a 'rocess stream hel's in utiliing the alua)le reactants to the ma8imum with minimum loss of reactants. B. &he ratio of the 9uantity of a reactant 'resent in the reactor feed of a recycling o'eration to the 9uantity of the same reactant entering the 'rocess as fresh feed is called com)ined feed ratio. C. Recyclin% in a process does not !elp in %ettin% !i%!er ex tent o reaction. . 2ecycling is e8em'lified )y reflu8ing )ac/ a 'art of the distillate to the distillation column to maintain the 9uantity of li9uid within the column.
3#. Which of the following graity scales is used e8clusiely for li9uids heaier than water? $. Baumme scale C. $#! scale B. &addel scale . none of these 36. 2ecycling in a chemical 'rocess facilitates $. increased yield B. enrichment of 'roduct
C. heat conseration ,. all a ' c
37. Solutions haing the same osmotic 'ressure are called solutions. C. isotonic $. dilute B. ideal . Saturated 3(. Which of the following has the least effect on the solu)ility of a solid in a li9uid solent? C. pressure $. tem'erature B. nature of the solent . nature of the solute 3*. &he a)ility of one li9uid to dissole in another is calledG $. hydro'hilicity C. an e8'anded solent B. misci'ility . the solation energy "0. #ic/ out the wrong statement.
$. &o ma/e (,, /g of a solution containing 4,> salt )y mi8ing solution $ containing 5> salt@ and solution B containing 5,> salt@: the amount of solution $ re9uired is 4, /g. B. (. gm atoms of car)on and (.5 gm moles of o8ygen are reacted to gie ( gm mole of car)on dio8ide. &he limiting reactant is car)on. &he 'ercent e8cess reactant su''lied is 5. C. $ gas )u))le at a 'ressure of #g is 'assed through a solent with a saturation a'or 'ressure of #s. !f the time of 'assage of the )u))le is long and air is insolu)le in the solent: the mole fraction of solent in the )u))le will )e e9ual to #s1#g. ,. A supersaturated solution o a sparin%ly solu'le solute at a concentration o C is 'ein% ed to a crystalli8er at a +olumetric lo& rate o 9. !e solu'ility o t!e solute is C1. !e output rate o solids rom an eicient crystalli8er is C : C1 9.
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CHE CALCULATIONS 1 PROBLEM SOLVING "1. !f ( L of ethyl alcohol is mi8ed with l L of water.How many /ilograms of solution result and how many cu)ic centimeter? Ans. 17(7 %rams 1*23 cm3 "2. $ li9uid adhesie: which is used to ma/e laminated )oards: consists of a 'olymer dissoled in a solent. &he amount of 'olymer in the solution has to )e carefully controlled for this a''lication. When the su''lier of the adhesie receies an order for -,,, /g of an adhesie solution containing (- wt > 'olymer: all it has on hand is (@ 5,, /g of a (, wt > solution: @ a ery large 9uantity of a , wt > solution: and -@ 'ure solent. Calculate the weight of each of the stoc/s that must )e )lended together to fill the order. "se all of the (, wt > solution. Ans. B; 1700 4% C; (00 4% $in4ed )ro'lem "3 "" ou are as/ed to measure the rate at which waste gases are )eing discharged from a stac/. &he gases entering contain .( > car)on dio8ide. #ure car)on dio8ide is introduced into the )ottom of the stac/ at a measured rate of 4., l) 'er minute. ou measure the discharge of gases leaing the stac/: and find the concentration of car)on dio8ide is -. >. "3. Calculate the rate of flow: in l) mol1minute: of the entering waste gases. Ans. <; (.01 l'mol/min "". Calculate the rate of flow: in l) mol1minute: of the 'roduct. Ans. <; (.10 l'mol/min "#. $ laundry can 'urchase soa' containing -,., wt > water at a 'rice of I +.,, 'er /g. &he same manufacturer offers a soa' containing 5., wt > water. !f the freight rate is I 6.,, 'er (,, /g: what is the ma8imum 'rice that the laundry should 'ay the manufacturer for the soa' containing 5., wt > water ? 3ote that the )uyer has to 'ay the freight. Ans. = *.#2 / 4% &et soap $in4ed )ro'lem "6 > "7 $ crystallier contains 64, l) of a9ueous solution of anhydrous sodium sulfate concentration F.6 wt >@ at (,4 *C. &he solution is cooled to , *C to crystallie out the desired 3aSJ4. (, HJ. &he remaining solution the mother li9uor@ is found to contain (6.( > anhydrous sodium sulfate. "6. What is the weight of this mother li9uor? Ans. 3300 l' "7. What is the weight of the #roduct? Ans. 3100 l'
$in4ed )ro'lem "( "* $ tri'le effect ea'orator is designed to reduce water from an incoming )rine 3aCl KHJ@ stream from 5 wt > to wt >. !f the ea'orator unit is to 'roduce (4:6+, l)1hr of 3aClalong with - wt > HJ@.
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CHE CALCULATIONS 1 "(. etermine the feed rate of )rine in l)1hr. Ans. #6*00 l'/!r "*. etermine the water remoed from the )rine in each ea'orator. Ans. 13(00 l'/!r $in4ed )ro'lem #0#2 $ contact sulfuric acid 'lant 'roduces FA., > sulfuric acid: )y a)sor)ing SJ- into a F+.-> sulfuric acid solution. $ gas containing A.,, > SJ- remainder inerts@ enters the SJ- a)sor'tion tower at the rate of A l) mol 'er hour. FA.5 > of the SJ- is a)sor)ed in this tower. F+.- > sulfuric acid is introduced into the to' of the tower and F5.F > sulfuric acid from another 'art of the 'rocess is used as ma/e < u' acid. &he flow sheet is gien in the figure with all of the /nown data on it. #0. Calculate the l)1day of F5.F > HSJ4 ma/e HSJ4 solution introduced into the to' of the tower. Ans. 6"70 l'/day #2. Calculate the l)1day of FA > HSJ4 solution 'roduced. Ans. 22"0 l'/day $in4ed )ro'lem #3 > #6 #erchloric acid HClJ 4@ can )e 're'ared as shown in the diagram )elow from BaClJ4@ and HClJ4. Sulfuric acid is su''lied in ,> e8cess to react with BaClJ4@. !f (+:4,, l) HClJ4 leae the se'arator and the recycle is 6(5 l) BaClJ 4@ oer the time 'eriod: calculate G 3ote G , > HSJ4 is )ased on the total BaClJ4@ entering the reactor. BaClJ 4@ K HSJ4 <<<<<< BaSJ4 K HClJ4 7WG BaClJ4@ --6M BaSJ4 --M HSJ4 FAM HClJ4 (,,. #3. &he oerall conersion of BaClJ 4@. Ans. 100#". &he l) of HClJ 4 leaing the se'arator 'er l) of feed. Ans. 0.6" l' ?Cl@ " / l' < ##. &he l) of HSJ4 entering the reactor. Ans. 10700 l' #6. &he 'er 'ass conersion of BaClJ4@. Ans. ;0.(0 $in4ed )ro'lem #7#( &he feed to a distillation column is se'arated into net oerhead 'roduct containing nothing with a )oiling 'oint higher than iso)utane and )ottoms containing nothing with a )oiling 'oint )elow that of 'ro'ane. &he com'osition of the feed is mole % Ethylene ., Ethane -., #ro'ylene 5., #ro'ane (5., !so)utane 5., n
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CHE CALCULATIONS 1 $in4ed )ro'lem #*60 !f (,,g of 3aSJ4 is dissoled in ,,g of H J and the solution is cooled until (,, g of 3aSJ4N(,HJ crystallies out: find #*. &he com'osition of the remaining solution mother li9uor@. Ans. a25@" 2(- ?2@ 7260. &he grams of crystals recoered 'er (,, g of initial solution. Ans. 33.3 % crystals/100 % solution $in4ed )ro'lem 61 6" $ solent dewa8ing unit in an oil refinery is se'arating -,,, ))l1day of a lu)ricating distillate into - ol 'ercent of slac/ wa8 and ++ ol 'ercent of dewa8ed oil. &he charge is mi8ed with solent: chilled: and filtered into wa8 and oil solution streams. &he solent is then remoed from the two streams )y two )an/s of stri''ing columns: the )ottoms from each column in a )an/ )eing charged to the ne8t column in the )an/. &he oil )an/ consists of four columns: and the wa8 )an/ of three. $ test on the charge and )ottoms from each column gae the following resultsG percent solvent by volume to 1st column
no. 1 bottoms
no. 2 bottoms
no. 3 bottoms
no. 4 bottoms
#ressed oil
A-
+,
+
4.,
,.A
Wa8
A-
+(
-
,.5
O
61.
Calculate the total solution 'er day charged to the whole unit. Ans. 176#0 ''l/day 62. #ercentage of total solent in oil solution remoed )y each column in oil )an/. Ans. 1 #2."#- 2 "0.20- 3 6.67- " 0.6(63. #ercentage of total solent in wa8 solution remoed )y each column in wa8 )an/. Ans. 1 "*.*- 2 "".0#- 3 6.0#- " 22.1"6". Barrels of solent lost 'er day in )ottoms from last column of each )an/@. Ans. 22.1" ''l/day 6#. 7any chemicals generate emissions of olatile com'ounds that need to )e controlled. !n the 'rocess shown in the accom'anying figure: the CJ in the e8haust is su)stantially reduced )y se'arating it from the reactor effluent and recycling the unreacted CJ together with the reactant. $lthough the 'roduct is 'ro'rietary: information is 'roided that the fresh feed stream contains 4,> reactant: 5, > inert and (, > CJ: and that on reaction moles of reactant yield .5 moles of 'roduct. Conersion of the reactant to 'roduct is +- > on one 'ass through the reactor: and F, > for the oer all 'rocess. &he recycle stream contains A,> CJ and ,> reactant. Calculate the ratio of moles of the recycle stream to moles of the 'roduct stream. Ans. 3.# 66. #a'er 'ul' is sold on the )asis that it contains ( ' ercent moistureM if the moisture e8ceeds this alue: the 'urchaser can deduct any charges for the e8cess moisture and also deduct for the f reight costs of the e8cess moisture. $ shi'ment of 'ul' )ecame wet and was receied with a moisture content of 'ercent. !f the original 'rice for the 'ul' was I4,1ton of airdry 'ul' and if the freight is I(.,,1(,, l) shi''ed: what 'rice should )e 'aid 'er ton of 'ul' deliered? Ans. =#1.*0 / ton
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CHE CALCULATIONS 1 $in4ed )ro'lem 67 > 6( $cetic acid is to )e generated )y the addition of (, 'ercent e8cess sulfuric acid to calcium acetate. &he reaction → Ca$C@ K HSJ4 CaSJ4 K H$c goes on with F, 'ercent com'letion. &he unused Ca$c@ and the HSJ4 are se'arated from the 'roducts of thereaction: and the e8cess Ca$c@ is recycled. &he acetic acid is se'arated from the 'roducts.
67. Pind the amount of recycle 'er hour )ased on (,,, l) of feed 'er hour. Ans. 111 l' CaAC 2 / !r 6(. Pind the 'ounds of acetic acid manufactured 'er hour. Ans. 760 l' ?Ac/!r $in4ed )ro'lem 6*72 &he reaction of ethyl
Based on the CHBr 4: on one 'ass through the reactor the conersion is A,>: and the unreacted CHBr 4 is recycled. Jn the )asis of l,,, /g of C HBr 4 fed to the reactor 'er hour. 6*. How much CH is 'roduced 'er hour in l)@ Ans. 7#.1 4% C 2?2 70. the rate of recycle in l)1hr Ans. 2#0 4% 71. the amount of Qn that has to )e added 'er hour if Qn is to )e ,> in e8cess Ans. "#" 4% 72. the mole ratio of QnBr to CH in the 'roducts. Ans. 2 73. $n organic ester of formula C(FH-6J is to )e hydrogenated at a rate of (,, /g1h to yield C(FH-AJ. &he hydrogen re9uired for the 'lant: which run continuously: is aaila)le as 5,L cylinders in which the gas is contained at +, )ar and -,, R. How many cylinder should the com'any order 'er wee/? Ans. "0"."( ~ "0# 7". #icric $cid is o)tained )y nitrating 'henol according to the reactionG 6 5+33⟶ 6 2(2)3+3 2
!n a 'articular o'eration: (,, /g 'henol was reacted with 5, /g H3J - to 'roduce ,, /g 'icric acid. Pind the com'osition of the 'roduct stream )y > weight. Ans. 6 2 23 > #7.1#- 6 # > #.11- 3 > 2".26- 2 > 13."(-
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CHE CALCULATIONS 1 $in4ed )ro'lem 7# 76 (:,,, /g1h of a fruit ;uice with (,> solids is freee solids. &he diluted ;uice is fed to a freeer where ice crystals are formed and then the slush is se'arated in a centrifugal se'arator into ice crystals and concentrated ;uice. $n amount of 5,, /g1h of li9uid is recycled from these se'arator to the freeer. 7#. Calculate the amount of ice that is remoed in the se'arator Ans. 7#0 4%/!r 76. &he amount of concentrated ;uice 'roduced. Ans. 2#0 4%/!r $in4ed )ro'lem 77 > 7* anthan gum is 'roduced using Xanthomonas campestris in a )atch culture. La)oratory e8'eriments hae shown that for each gram of glucose utilied )y the )acteria: ,.- g o8ygen and ,.,( g ammonia are consumed while ,.+5 g gum: ,.,F g cell: ,.+ g gaseous CJ: and ,.(- g HJ are formed. Jther com'onents such as 'hos'hate can )e neglected. $ medium containing glucose and ammonia dissoled in ,:,,, liters of water is 'um'ed into the CS&2 fermenter and inoculated with X. campestris. $ir is 'um'edM the off gas recoered during the entire )atch is (:5, /g. &he final gum concentration is -.5 > wt. 77. What is the 'ercentage of e8cess air: Ans. 2#.(0 7(. How much glucose are re9uired? Ans. *7(.2(7 4% 7*. How much ammonia are re9uired? Ans. *.("6 4% (0. &he ground nut seeds containing 45> oil and 45> solids are fed to e8tractor: the ca/e coming out of e8tractor is found to contain A,> solids and 5> oil. Pind the 'ercentage recoery of oil. Ans. *3.7#$in4ed )ro'lem (1(2 $ , weight > solution of 3aSJ4 at ,,*P is 'um'ed continuously to a acuum crystallier from which the magma is 'um'ed at 6,*P. (1. What is the com'osition of this magma? Ans. C (.0(#"- $ *1.*1"6(2. What 'ercentage of 3aSJ4 in the feed is recoered as 3a SJ4N(,HJ crystals after this magma is centrifuged? Ans. 17.(3(3. $ 'lant 'roduces -,:,,, 7& of anhydrous sulfate annually )y crystalliing sulfate )rine at ,*C: yields of F5> and F,> in the crystalliation and calcinations o'erations are o)tained res'ectiely. How many metric tons of li9uor are fed to the crystallier daily? 3oteG -,, wor/ing days 'er year. Ans. <; #012.6 /day $in4ed )ro'lem (" (6 Presh air containing 4.,, mole> water a'or is to )e cooled and dehumidified to a water content of (.+, mole> HJ.$stream of fresh air is com)ined with a recycle stream of 'reiously dehumidified air and 'assed through the cooler. &he )lended stream entering the unit contains .-, mole> HJ. !n the air conditioner: some of the water in the feed stream is condensed and remoed as li9uid. $ fraction of the dehumidified air leaing the cooler is recycled and the remainder is deliered to a room. &a/ing (,, mol of dehumidified air deliered to the room as a )asis of calculation. (". Calculate the moles of fresh feed. Ans. 102." moles res! eed (#. 7oles of water condensed. Ans. 2." moles o &ater condensed (6. 7oles of dehumidified air recycled. Ans. 2*0 mole recycled
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CHE CALCULATIONS 1 $in4ed )ro'lem (7*0 7ethanol is 'roduced in the reaction of car)on dio8ide and hydrogenG C@2:3?2⟶C?3@? : ?2@ &he fresh feed to the 'rocess contains hydrogen: car)on dio8ide: and ,.4,, mole> inerts !@. &he reactor effluent 'asses to a condenser that remoes essentially all of the methanol and water formed and none of the reactants or inerts. &he latter su)stances are recycled to the reactor. &o aoid )uildu' of the inerts in the system: a 'urge stream is withdrawn from the recycle. &he feed to the reactor not the fresh feed to the 'rocess@ contains A., mole> CJ +,., mole> H: and .,, mole> inerts. &he single<'ass conersion of hydrogen is 6,.,>. (7. Calculate the molar flow rates and molar com'ositions of the fresh feed. Ans. 2*0 mole recycled ((. Calculate the total feed to the reactor. Ans. 2*0 mole recycled (*. Calculate the recycle stream. Ans. 2*0 mole recycled *0. Calculate the 'urge stream for a methanol 'roduction rate of (55 /mol CH -JH1h. Ans. 2*0 mole recycled $in4ed )ro'lem *1*2 &wo li9uid streams are flowing at constant rates into a )lender. Jne is )enene: which flows at a measured rate of ,., L1min: and the other is toluene. &he )lended mi8ture enters a storage tan/ inner diameterD 5.5 m@ e9ui''ed with a sight gauge. uring an interal in which no li9uid leaes the storage tan/: the li9uid leel in the tan/ is o)sered to increase )y ,.(5 meters oer a one )enene@. Ans. 3"$in4ed )ro'lem *3*# Li9uid e8traction is an o'eration used to se'arate the com'onents of a li9uid mi8ture of two or more s'ecies. !n the sim'lest case: the mi8ture contains two com'onentsG a solute $@ and a li9uid solent B@. &he mi8ture is contacted in an agitated essel with a second li9uid solent C@ that has two /ey 'ro'ertiesG $ dissoles in it: and B is immisci)le or nearly immisci)le with it. Por e8am'le: B may )e water: C a hydrocar)on oil: and $ a s'ecies that dissoles in )oth water and oil.@ Some of the $ transfers from B to C: and then the B
*3. What is the ma8imum num)er of inde'endent material )alances that can )e written for this 'rocess? Ans. 3 *". Calculate mC: mE: and m2: using the gien mi8ture feed rate as a )asis and writing )alances in an order such that you neer hae an e9uation that inoles more than one un/nown aria)le. Ans. mC ; "17%/min m ; "61 %/min m R ; 3#6 %/min *#. Calculate the difference )etween the amount of acetic acid in the feed mi8ture and that in the ,.5> mi8ture: and show that it e9uals the amount that leaes in the F.6> mi8ture. Ans. "" %/min
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CHE CALCULATIONS 1 *6. Straw)erries contain a)out (5 wt> solids and A5 wt> water. &o ma/e straw)erry ;am: crushed straw)erries and sugar are mi8ed in a 45G55 mass ratio: and the mi8ture is heated to ea'orate water until the residue contains one< third water )y mass. Calculate how many 'ounds of straw)erries are needed to ma/e a 'ound of ;am. Ans. 0."* l' o stra&'erries *7. &hree hundred gallons of a mi8ture containing +5., wt> ethanol ethyl alcohol@ and 5> water mi8ture s'ecific graity ,.A++@ and a 9uantity of a 4,., wt> ethanol6,> water mi8ture S0 ,.F5@ are )lended to 'roduce a mi8ture containing 6,., wt> ethanol. &he o);ect of this 'ro)lem is to calculate 4,: the re9uired olume of the 4,> mi8ture. Ans. 207 %allons $in4ed )ro'lem *(100 &wo a9ueous sulfuric acid solutions containing ,., wt> HSJ4 S0 ( (-F@ and 6,., wt>H SJ4S0 D(.4FA@ are mi8ed to form a 4.,, molar solution S0 D (.(-@. *(. Calculate the mass fraction of sulfuric acid in the 'roduct solution. Ans. 0.323 **. &a/ing (,, /g of the ,> feed solution as a )asis: draw and la)el a flowchart of this 'rocess:la)eling )oth masses and olumes: and do the degree solution1liter 6,> solution@. Ans. 2.*6 100. What feed rate of the 6,> solution L1h@ would )e re9uired to 'roduce (5, /g1h of the 'roduct? Ans. 2#7 $/!r
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