Answers 1984 Free Response

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Advanced Placement Chemistry: 1984 Free Response Answers

• [delta] and [sigma] are used to indicate the capital Greek letters.

• [square root] applies to the numbers enclosed in parenthesis immediately following

• All simplifying assumptions are justified within 5%.

• ne point deduction for a significant figure or math error! applied only once per problem.

• "o credit earned for numerical answer without justification.

• ther correct ways of sol#ing the problems recei#ed full credit. $ecause of limitations of space! such other

solutions are not shown.

& A#erage score '.()a& two points p* + ,.)-[*] + / -0 ,.)- 1 + 2.5 / -0 3 1

[*0] + 4 / -0

'

& 42.5 / -0

3

& 1+ '.- / -0 ) 1

b& three points6)*562 0 ** 7778 6)*562* *0 9 + 4[6)*562*][*0]& : [6)*562 0]+ 44'.- / -0 ,& 4'.- / -0 )&& : 4-.- 7 '.- / -0 )&+ .) / -0 -

c& one point6)*562* ;+++8 * 6)*562 0 9 a + 4[*][6)*562 0]& : [6)*562*]+ 442.5 / -0 3& 4-.-&& : 4'.- / -0 )&+ ).( / -0 5

d& two points6)*562* ;+++8 6)*562 0 *0 p* + 2.,,[* ] + / -0 2.,,1 + .( / -0 ( 9 a + 4[* ][6)*562 0]& : [6)*562*]).( / -0 , + 44.( / -0 (& 4.( / -0 (&& : /

/ + 2., / -0 2 1<otal 6)*562* in solution +42., / -0 2 .( / -0 (& 1 +2.3 / -0 2 1



2& A#erage score '.,

a& three points= one point for correct form of law and two points for correct methodology without an error= one pointfor correct methodology with an error >ate + k[?]

b& two [email protected] / -0 ' mole sec + k 4-.- mole &k + @.- / -0 ( sec0

c& two points

2.( log co c + k t2.( log -.)- -.'- + [email protected] / -0 (& 4t&t + 5, s

d& two point1echanism ( is correct.<he rate law shows that the slow reaction must in#ol#e one ?! consistent with mechanism (.1echanisms and 2 would in#ol#e both [B] and [?] in the rate law! not consistent with the rate law.

(& A#erage score 5.52

a& three pointsCrom *essDs lawE[delta]*Ff + [' 4(3(.5& ' 42-5.,5&] 7 2,(.5 k + 7 5((., k

b& one point' 64s& ' *24g& 24g& 7778 6(*@6*

c& two points[delta]HFf butyric acid + HF butyric acid 7 ' HF carbon 7 ' HF *2 7 HF 2

[delta]HFf butyric acid + [22).( 7 '45.)3& 7 '4(-.)& 7 2-5] joules9 + 7 52(.3 joules9 "oteE If part c was based on the equation in part b! and was done correctly! credit was gi#en for part c e#en if part b

was wrong.

d& three points[delta]GFf butyric acid + [delta]*Ff 7 < [delta]HFf

[delta]GFf + [7 5((.3 7 423,& 47 -.52'&] k[delta]GFf + 7 (@@.@ k "oteE Cor each of the problems! a ma/imum of one point was subtracted for gross misuse of significant figures and.or for a mathematical error if correct principles were used.



'& A#erage score (.52a& two pointsJater boils at a lower temperature in Ken#er than in "ew ?ork 6ity because the atmospheric pressure is less at highaltitudes.At a lower temperature! the cooking process is slower! so the time to prepare a hard7boiled egg is longer.

b& two pointsH 2 7778 H2 4as coal is burned&H2 *2 7778 *2H( 4in the atmosphere&H2 2 2 *2 7778 *2H' 4in the atmosphere&

c& two pointsLaporiMation or e#aporation of sweat from the skin.<hese processes are endothermic and so cool the skin.

d& two points6olligati#e properties! which depend on the number of particles present! are in#ol#ed.Holute 4the antifreeMe& causes the lowering of the #apor pressure of the sol#ent. Jhen the #apor pressure of thesol#ent is lowered! the freeMing point is lowered and the boiling point is raised.

5& A#erage score (.-5Noints awarded are indicated at the end of each statement.An indicator signals the endpoint of a titration by changing color. 42&An indicator is a weak acid or a weak base where the acid form and the basic form of the indicator are differentcolors. 42&An indicator usually changes color when the concentrations of the acid form and the basic form are about equal= that

is! when the p* is near the p9 for the indicator. 4&Jhen an indicator is selected! the p* at which the indicator changes color should bracket the p* of the titrationsolution at the equi#alence point. 42&Cor e/ample! when a strong acid is titrated with a strong base! the p* at the equi#alence point is @! so an indicatorthat changes color at a p* of @ should be used. 4&

)& A#erage score 2.)-<wo points 4to a ma/imum of eight& were awarded for each correct test with the e/pected results. Nossibilitiesinclude the followingE. Clame testE 9 la#ender= 4"*'&26(! no la#ender 2. Add 6l2and 6*26l2E 9I! pink color in organic layer= 4"*'&26(! no change(. Add Nb2E 9I! yellow precipitate of NbI2= 4"*'&26(! white precipitate of Nb6(

'. Add Ag

E 9I! pale yellow precipitate of AgI= 4"*'&26(! white precipitate of Ag26(5. Add I2E 9I! brown color of I( 0= 4"*'&26(! no change). Add good o/idiMing agentE 9I! brown color of I( 0= 4"*'&26(! no change@. Add strong baseE 9I! no changeE 4"*'&26(! odor of "*( or color change of red litmus,. Add $a2 or 6a2 or 1g2E 9I! no change= 4"*'&26(! with precipitate of a carbonate3. Kissol#e salts and use litmusE 9I! neutral= 4"*'&26(! basic solution-. Add nono/idiMing acidE 9I! no change= 4"*'&26(! bubbles of 62

. <est melting pointsE 9I! high= 4"*'&26(! decomposes before melting



@& A#erage score '.2,Noints awarded for each statement follow that statement.6onstant a is related to the attracti#e forces that e/ist between real molecules. 4 point&6onstant b is related to the fact that real molecules do ha#e #olumes. 4 point&*2H has a larger #alue for a. 4 point&*2H is a polar molecule and! therefore! has stronger intermolecular forces. 42 points&*2H has a larger #alue for b because an *2H molecule has a larger #olume than *2 has. 4 point&<he constant a correlates with the boiling point since a is related to the intermolecular forces! which must beo#ercome in the process of boiling a liquid. 42 points&

,& A#erage score '.)

Nhysical propertiesE 1etals "onmetals

1elting points >elati#ely high >elati#ely low

Olectrical conducti#ity Good Insulators

uster *igh ittle or none

Nhysical state 1ost are solids Gases! liquids! or solids

6hemical propertiesE 1etals "onmetals

redo/ >educing agents/idiMingor reducing agents

attraction to electrons Olectropositi#e Olectronegati#e

acidbase character/ides basicor amphoteric

/ides acidic

reacti#ity >eact with nonmetals>eact with both metalsand nonmetals

Olectron configurations 4 point each statement&E 1etalsE Lalence electrons in s or d suble#els of their atoms. 4A few hea#y elements ha#e atoms with one or two electrons in p suble#els.& "onmetalsE Lalence

electrons in the s and p suble#els of their atoms.<here are more metals than nonmetals because filling d orbitals in a gi#en energy le#el in#ol#es the atomsof ten element and filling the f orbitals in#ol#es the atoms of ' elements. In the same energy le#els! thema/imum number of elements with atoms recei#ing p electrons is si/.

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Answers 1984 Free Response