Experiment 3: Sublimation and Melting Point Determination 2BMT, Group 3, Dy, N.D.G., Gurion, R., Hernandez, A.M., Isidro, D.J., Lopez, J. and Macababbad, E.M. Departent o! "#arac$, %acu&t$ o! "#arac$, 'ni(ersit$ o! )anto Toas, Espa*a Bou&e(ard, ++- Mani&a, "#i&ippines
ABSTA!T In t#is eperient, a sap&e o! Benzoic acid /as puri!ied b$ et#od o! sub&iation. T#is process in(o&(es turnin0 t#e sap&e !ro its so&id p#ase to its 0aseous p#ase, /it#out #a(in0 to pass t#rou0# t#e &i1uid p#ase. A!ter t#at, t#e sap&e /as subected to t#e (aporizationso&idi!ication c$c&e, /#ic# turned it into sa&&, need&e&i4e cr$sta&s ca&&ed t#e sub&iate. Me&tin0 point /as t#en deterined b$ use o! oi& bat#. Resu&ts s#o/ t#at t#e sub&iate starts to e&t at ++5 67 and stops at +2 67, /#i&st t#e pure sap&e starts to e&t at +2 67 and stops at +22 67, s#o/in0 t#at t#e pure Benzoic acid #as a s&i0#t&$ #i0#er (apor pressure as copared to t#e t#e sub&iate.
"NT#D$!T"#N "uri!ication b$ sub&iation is a c#eica& process used used to sepa separa rate te non( non(o& o&at ati& i&ee ipu ipuri riti ties es !ro !ro (o&ati&e (o&ati&e copounds copounds.. T#e process process o! sub&iati sub&iation on in(o&(es #eatin0 an or0anic copound so t#at it 0oes !ro a so&id p#ase to a 0aseous or (apor state /it#ou /it#outt 0oin0 0oin0 t#rou t#rou0# 0# t#e t#e &i1ui &i1uid d p#ase. p#ase. T#is T#is sub& sub&i iat atio ion n proce rocesss can be use!u se!u&& !or !or t#e puri!ication o! or0anic copounds, suc# as cap#or, sa&ic$&ic acid and benzoic acid. Ho/e(er, t#e proces processs is uti&i uti&ized zed /#en /#en t#e copou copound nd #as 8+9 non(o&ati&e ipurities. T#e T#e e&tin e&tin0 0 point point o! a subst substanc ancee is t#e teperature at /#ic# t#e substance c#an0es !ro a so&id to a &i1uid state. Me&tin0 point is one /a$ to deterine t#e purit$ o! a substance, due to t#e !act t#at e(en sa&& 1uantities o! ipurities can a!!ect a substance:s substance:s e&tin0 point. 829 T#e obecti(e obecti(ess o! t#is eperient eperient are; <+= to puri!$ t#e ipure benzoic acid t#rou0# sub& sub&i iat atio ion, n, <2= <2= to ca&c ca&cu& u&at atee t#e t#e perc percen enta ta0e 0e reco(e reco(er$ r$ o! t#e t#e benzo benzoic ic acid acid a!ter a!ter sub&i sub&iati ation, on, and and <3= <3= to iden identi ti!$ !$ t#e t#e e&t e&tin in0 0 poin points ts o! t#e t#e sub&iate and t#e pure benzoic acid t#rou0# t#e use o! an oi& bat#.
MET%#D#&#G'
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To start t#e process o! o! sub&iation, -0 o! o! ipure benzoic acid /as /ei0#ed in a pre/ei0#ed e(ap e(apor orat atin in0 0 dis# is# and and t#en co(e co(erred /it# /it# a per!orated !i&ter paper. An in(erted /atc# 0&ass, /#ic# /as pre/ei0#ed, as4in0 tape /as used to 4eep it attac#ed to t#e e(aporatin0 dis# and to 4eep an$ oisture oisture !ro escapin0. escapin0. A oistened oistened tissue tissue paper /as put on top o! t#e /atc# 0&ass. It /as a&&o/ed to #eat in a #ot p&ate !or +- inutes. A!ter coo&in0 it to roo teperature, t#e sub&iate !ound in t#e in(erted /atc# 0&ass and per!orated !i&ter paper /ere co&&ected and /ei0#ed in t#e /ei0#in0 sca&e. sca&e. %ro %ro t#e data data co&&ec co&&ected ted,, t#e percen percenta0 ta0ee reco(e reco(er$ r$ /as ca&cu& ca&cu&ate ated. d. %or deter deterina inatio tion n o! e&tin0 point, t#e sub&iate /as 0round into a !ine po/der usin0 a ortar and a pest&e, a!ter /#ic# it /as pac4ed into a capi&&ar$ tube. To ensure t#at t#e po/der is ti0#t&$ pac4ed to0et#er, to0et#er, t#e c&osed end o! t#e capi&&ar$ tube /as dropped se(era& ties in a 0&ass tubin0 unti& it /as /e&&pac4ed /it# 3- o! t#e sub&iate. A sap&e o! pure benzoic acid /as a&so /ei0#ed and pac4ed !or re!erence. A!ter asseb&$ o! an oi& bat# setup, t#e capi&&ar$ tubes /ere t#en stuc4 to a t#eroeter /it# its c&osed end attac#ed to t#e ercu rcur$ bu&b o! t#e t#eroeter usin0 a as4in0 tape. Iersin0 t#e capi&&ar$ tubes into t#e bat#, t#e sap&es #eated up. T#e teperature at /#ic# bot# copounds started to e&t e&t and and t#e te tepera peratu ture re at /#ic /#ic# # bot# bot# #a(e cop&ete&$ e&ted /as t#en recorded.
ES$&TS AND D"S!$SS"#N )ub&iation )ub& )ub&i iat atio ion n is ep&o ep&o$ $ed as a ean eanss o! puri!ication o! certain substances, /#ic# are #eated in c&osed containers. In ost cases, t#e teperature does not eceed a &o/ red #eat. Dissociation o!ten occurs occurs in t#e process. process. 839 Tab&e + describes t#e data
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Benzoic acid -. 0 >ei0#t o! >atc# 0&ass ? sub&iate
[email protected] 0 >ei0#t o! >atc# 0&ass
ei0#t o! )ub&iate .- 0 Table 1. Data collected from sublimation. %ro t#e data co&&ected, co&&ected, t#e percenta0e reco(er$ reco(er$ can be !ound usin0 t#e !oru&a;
Reco(er$
C
Weight of sublimate × 100 Weight of impure impure Benzoic acid
0.5 g
Reco(er$ C 5.0 g
× 100
Reco(er$ C + Ipure benzoic acid, acid, as t#e nae nae ip&ies, ip&ies, is t#e crude !or o! benzoic acid. T#e ipurities o! t#is crude !or are p#t#a&ic acid and benz$&benzoate. 7oputation o! percenta0e reco(er$ is essentia& because it s#o/s us #o/ ipure t#e substance /as, and and #o/ #o/ accu accura rate te /e /ere /ere in !o&& !o&&o/ o/in in0 0 t#e t#e procedures o! puri!ication. puri!ication. Based on on t#e resu&ts obtained !ro Tab&e Tab&e +, and !ro ca&cu&ation o! percenta0e reco(er$, it s#o/s t#an o! t#e initia& sap&e /as ade up o! ipurities. Me&tin0 "oint Deterination Me&tin0 point re!ers to t#e teperature at /#ic# /#ic# a substance turns !ro its so&id p#ase to its &i1uid p#ase. It is a sip&e and !ast /a$ to deterine #o/
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A!ter iersion o! t#e capi&&ar$ tubes into t#e oi& bat# set up, t#e teperature at /#ic# it e&ts /as recorded. Tab&e Tab&e 2 s#o/s t#e teperature at /#ic# it starts to e&t, and /#ere it stops.
Teperature + re r eadin0 2nd Readin0 st
A(era0e
"ure Benzoic +267 +2267 +2+67 acid )ub&iate ++567 +267 ++67 Table 2. Data Data collec collected ted from from meltin melting g point point determination. Based on t#e data 0at#ered, 0at#ered, t#ere is a 2 di!!erence bet/een t#e standard e&tin0 point and t#e e&tin0 point o! t#e sub&iate. T#is a$ be due to &e!to(er ipurities !ro is#and&in0 and containation.
E(EEN!ES Organic Laboratory Techniques .
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