PAUAcidoBase resuelto.pdf

7/25/2019 PAUAcidoBase resuelto.pdf

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Qumica P.A.U. CIDOS Y BASES 1

CIDOS Y BASES

PROBLEMAS

CIDO/BASE DBIL

1. Una disolucin de aon!aco de concen"#acin $%$1 ol/d&es"' ioni(ada en un )%*+.a, Esc#i-a la #eaccin de disociacin calcule la concen"#acin ola# de cada una de las ese0

cies eis"en"es en la disolucin una 2e( alcan(ado el e3uili-#io.-, Calcule el 4 la K-del aon!aco.

(P.A.U. Jun. 11)

Rta.:a) [NH3] = 0,0096 mol/dm3; [OH] = [NH4+] = 4,210-4mol/dm3; b) pH = 10,6;Kb= 1,810-5

Datos Cifras significativas: 3

o!"#!$%a"&'! d# la d&(ol"&'! d# amo!*a"o [NH3]0= 0,0100 mol/dm3

%ado d# &o!&a"&'! d#l NH3#! la d&(ol"&'! = 4,20. = 0,0420%od"$o &'!&"o d#l aa K= [H+][OH] = 1,00 1014

Incgnitas

o!"#!$%a"&'! d# "ada !a d# la( #(p#"( p%#(#!$#( #! la d&(ol"&'! [NH3], [OH], [NH4+], [H+]

pH d# la d&(ol"&'! pH

o!($a!$# d# ba(&"&dad d#l NH3 Kb

Otros smbolos

&(ol"&'! D

o!"#!$%a"&'! mol/dm3

) d# ba(# db&l # (# d&(o"&a xa!$&dad d# la (($a!"&a 7 n7)

Ecuaciones

o!($a!$# d# ba(&"&dad d# la ba(# OH)baq) b+aq) + bOH aq) Kb=[+ b]

e[OH-]

e

b

[OH)b ]e

pH pH = lo[H+]

%od"$o &'!&"o d#l aa pH + pOH = 14

Solucin:

a) omo #l amo!*a"o #( !a ba(# db&l, (# d&(o"&a%: #! aa (#! la #"a"&'!

NH3aq) + H2O NH 4+ aq) + OHaq)


2/37


[OH]#= [NH4+]#= [NH3]d= 4,2010-4moldm-3

@a "o!"#!$%a"&'! d# &o!#( &d%'#!o (# "al"la d#l p%od"$o &'!&"o d#l aa

[H+ ]#= K

[OH]=

1,001014

4,20104=2,381011 moldm3

b) &do [OH]

Otros smbolos

&(ol"&'! D

o!"#!$%a"&'! mol/dm3) d# :"&do db&l # (# d&(o"&a x

a!$&dad d# la (($a!"&a 7 n7)

Ecuaciones

o!($a!$# d# a"&d# d#l :"&do HaG aq) aH+aq) + Ga aq) Ka=[H+]

e

a [Ga-]e

[Ha G ]e

pH pH = lo[H+]

%od"$o &'!&"o d#l aa pH + pOH = 14

Solucin:

a) omo #l :"&do Dlo%*d%&"o #( ! :"&do db&l, (# d&(o"&a%: #! aa (#! la #"a"&'!

HE aq) H + aq) + Eaq)


3/37


="a!$&dadd&(o"&ada

"a!$&dad &!&"&al =

"o!"#!$%a"&'!d&(o"&ada

"o!"#!$%a"&'! &!&"&al

#l %ado d# &o!&a"&'! (# "al"la la "o!"#!$%a"&'! d# :"&do Dlo%*d%&"o d&(o"&ado

[HE]d= [HE]0= 0,400 2,5010-3moldm-3= 1,0010-3moldm-3

po% lo # la "o!"#!$%a"&'! d#l :"&do Dlo%*d%&"o #! #l #&l&b%&o #(

[HE]#= [HE]0 [HE]d= 2,5010-3moldm-3 1,0010-3moldm-3= 1,5010-3moldm-3

# la #($#&om#$%*a d# la d&(o"&a"&'!, la "o!"#!$%a"&'! d# &o!#( &d%'#!o la d# &o!#( Dlo%%o #( &al ala d# :"&do Dlo%*d%&"o d&(o"&ado?

[H+] = [E] = [HE]d= 1,0010-3moldm-3

@a "o!($a!$# d# #&l&b%&oKa#(

Ka=[H+ ]#[E

]#[HE]#

=1,00103 1,00103

1,50103 =6,6C104

b) 'nico ono#"ico de ca#'c"e# d?-il de 5#ula 4C@4O)en un 2aso con a>ua 6as"a cole"a# *7$ c&de disolucin% indi3ue9a, El 4 de es"a disolucin.-, El >#ado de disociacin del 'cido.Da"o9 Ka &%*81$;) (P.A.U. Jun. 08)Rta.:a) pH = 2,C; b) = 14.


Ia(a d# :"&do H9HCO4 m= 0,650

Jolm#! d# d&(ol"&'! %= 250 "m3= 0,250 dm3

o!($a!$# d# a"&d# Ka= 3,2C104

Incgnitas


%ado d# d&(o"&a"&'!

Otros smbolos


a!$&dad d# (($a!"&a &!&"&al n0

Ecuaciones


e

a [Ga-]e

[Ha G ]e

pH pH = lo[H+]

%ado d# d&(o"&a"&'! = nd/ n0


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Solucin:

a) @a ma(a mola% d#l :"&do H9HCO4#( 180 /mol?@a "a!$&dad d# :"&do # a #! 250 "m3d# d&(ol"&'! #(

n0H9HCO4) = 0,650 H9HCO4/ 180 H9HCO4/ mol H9HCO4) = 3,61103mol H9HCO4

po% lo # la "o!"#!$%a"&'! d# la d&(ol"&'! #(

[H9 HC O4]0=3,61103mol H

9H

CO

4

0,250dm3D

=0,0144mol /dm3

omo #( ! :"&do db&l mo!op%'$&"o, (# d&(o"&a%: #! aa (#! la #"a"&'!

H9HCO4aq) H+aq) + 9HCO4aq)

@lama!doxa la "o!"#!$%a"&'! d# :"&do # (# d&(o"&a, (# p#d# #("%&b&%o!"#!$%a"&'! H9HCO4 H+ 9HCO4

[ ]0 &!&"&al 0,0144 0 0 mol/dm3

[ ]d d&(o"&ada o Do%mada x K x x mol/dm3

[ ]# #! #l #&l&b%&o 0,0144 x x x mol/dm3@a "o!($a!$# d# #&l&b%&oKa#(

Ka=[

9H

CO

4

]#[H]

#

[H9 H C O4]#

L($&$#!do la( "o!"#!$%a"&o!#( #! #l #&l&b%&o

3,2C104= x & x

0,0144x

&ma"&'! (# p#d# (po!#% #x#( d#(p%#"&abl# D%#!$# a 0,0144 %#(olA#% la #"a"&'!

3,2C104 x

2

0,0144

# da

x0,0144 &3,2C104=2,1C103 mol/dm3

#%o al "al"la% #l %ado d# d&(o"&a"&'!

=[ :"&do d&(o"&ado ][:"&do &!&"&al ]

=2,1C103 mol/dm3

0,0144mol/dm3 =15.

(# A# # !o #( d#(p%#"&abl# po% lo # a # %#(olA#% la #"a"&'! d# (#!do %ado

x2+ 3,2C104x 4,C2106= 0

x= 2,02103mol/dm3

L# "al"la #l pH

pH = lo[H+] = lo2,02103) = 2,C0

b)


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Da"o9 Ka 1%$81$07 (P.A.U. Set. 08)Rta.:a) [H3OO]#= 1,34103mol/dm3; b) pH = 2,8C; = 1,34.


o!"#!$%a"&'! d# :"&do a"$&"o [H3OOH] = 0,100 mol/dm3

o!($a!$# d# a"&d# Ka= 1,80105

Incgnitas

o!"#!$%a"&'! d# &'! a"#$a$o [H3OO]


%ado d# d&(o"&a"&'!

Otros smbolos


a!$&dad d# (($a!"&a &!&"&al n0

Ecuaciones

o!($a!$# d# a"&d# d#l :"&do HaG aq) aH+aq) + Ga aq) Ka=[H+]e

a [G a-]e[H a G ]e

pH pH = lo[H+]

%ado d# d&(o"&a"&'! = nd/ n0

Solucin:

a)

=[ :"&do d&(o"&ado ][:"&do &!&"&al ]

=1,34103 mol/dm3

0,100mol /dm3 =1,34.


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(# A# # #( d#(p%#"&abl# po% lo # la (ol"&'! #( a"#p$abl#?

[H3OO] =x= 1,34103mol/dm3

b) L# "al"la #l pH

pH = lo[H+] = lo1,34103) = 2,8C

7. Conside#e una disolucin de aon!aco en a>ua de concen"#acin =%7$81$0*ol/d&.a, Calcule el 4 de es"a disolucin.-, Calcule el >#ado de disociacin del aon!aco en la disolucin.Da"o9 K-4&, 1%81$07 (P.A.U. Set. 11)Rta.:a) pH = 11,03; b) = 1,65.


o!"#!$%a"&'! d# la d&(ol"&'! d# amo!*a"o [NH3]0= 6,5010-2mol/dm3

o!($a!$# d# ba(&"&dad d#l NH3 Kb= 1,C810-5

%od"$o &'!&"o d#l aa K= [H+][OH] = 1,00 1014

Incgnitas


%ado d# d&(o"&a"&'! d#l NH3#! la d&(ol"&'!

Otros smbolos

&(ol"&'! D

o!"#!$%a"&'! mol/dm3) d# ba(# db&l # (# d&(o"&a x

a!$&dad d# la (($a!"&a 7 n7)

Ecuaciones

o!($a!$# d# ba(&"&dad d# la ba(# OH)baq) b+aq) + bOH aq) Kb=[+ b]e [OH

-]eb

[OH)b ]e

pH pH = lo[H+]

%od"$o &'!&"o d#l aa pH + pOH = 14

Solucin:

a) omo #l amo!*a"o #( !a ba(# db&l, (# d&(o"&a%: #! aa (#! la #"a"&'!


o!"#!$%a"&'! NH3 NH4+ OH

[ ]0 &!&"&al 6,5010-2 0 0 mol/dm3

[ ]d d&(o"&ada o Do%mada x x x mol/dm3

[ ]# #! #l #&l&b%&o 6,5010-2x x x mol/dm3

@a "o!($a!$# d# #&l&b%&oKb#(

Kb=[NH

4

+ ]e[OH-]

e

[NH3]e=

x & x

(6,50102x)=1,C8105

L&, #! p%&m#%a ap%o>&ma"&'!, "o!(&d#%amo( d#(p%#"&abl#xD%#!$# a 6,5010-2, la #"a"&'! (# %#d"# a

x=6,50102

&1,C8105=1,0810

3mol /dm

3

#, "ompa%ada "o! 6,5010-2#( d#(p%#"&abl#?


7/37


#ado de disociacin del aoniaco en la disolucinHDa"o9 K-4&, 1%81$07 (P.A.U. Set. 13)Rta.:a) [NH3]0= 3,0410-3mol/dm3; b) = C,3C.

Datos Cifras significativas: 3pH d# la d&(ol"&'! d# amo!*a"o pH = 10,35

o!($a!$# d# ba(&"&dad d#l NH3 Kb= 1,C810-5

%od"$o &'!&"o d#l aa K= [H+][OH] = 1,00 1014

Incgnitas

o!"#!$%a"&'! d# la d&(ol"&'! d# amo!*a"o [NH3]0


Otros smbolos

&(ol"&'! D


a!$&dad d# la (($a!"&a 7 n7)

Ecuaciones

o!($a!$# d# ba(&"&dad d# la ba(# OH)baq) b+aq) + bOH aq) Kb=[+ b]e [OH

-]eb

[OH)b]e

pH pH = lo[H+]

pOH pOH = lo[OH]

%od"$o &'!&"o d#l aa pH + pOH = 14

Solucin:

a) G pa%$&% d#l pH pod#mo( "al"la% #l pOH


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pOH = 14 pH = 14 10,35 = 3,65

d# a* la "o!"#!$%a"&'! d# &o!#( &d%'>&do #! #l #&l&b%&o?

[OH] = 10-pOH= 10-3,65= 2,2410-4mol/dm3

omo #l amo!*a"o #( !a ba(# db&l, (# d&(o"&a%: #! aa (#! la #"a"&'!


L& llamamo( c0a la "o!"#!$%a"&'! d# amo!*a"o a!$#( d# d&(o"&a%(#, xa la "o!"#!$%a"&'! d# amo!*a"o #(# d&(o"&a

o!"#!$%a"&'! NH3 NH4+ OH

[ ]0 &!&"&al c0 0 0 mol/dm3


[ ]# #! #l #&l&b%&o c0x x 2,2410-4 mol/dm3

#da #

x= 2,2410-4mol/dm3

@a "o!($a!$# d# #&l&b%&oKb#(

Kb=[NH4

+ ]e[OH-]e

[NH3]e=

x & x(c0x)

=x2

(c0x )= (2,24104)2

(c02,24104)

=1,C8105

#(p#a!do c0

c0=(2,24104)2

1,C8105 +2,24104=3,04103 mol/dm3

b) ua 11%* d&de 4&g, edidos a 1 a"s5e#a de #esin *7 $C o-"eni?ndo0se 1 d&de disolucin.a, 4alla la concen"#acin del 4&en la disolucin.-, De"e#ina la concen"#acin de 4) O4;en la disolucin.c, Calcula el 4 de la disolucin #esul"an"e.Da"os9 K- 1%1$07. (P.A.U. Set. 96)Rta.: a) [NH3]#= 0,46 mol/dm3; b) [NH4+]# = 2,9103 mol/dm3; [OH]# = 2,9103 OH mol/dm3;

") pH = 11,5


a( Aolm#! %= 11,2 dm3NH3

p%#(&'! (= 1,00 a$m?

$#mp#%a$%a )= 25 0 = 298

Jolm#! d# la d&(ol"&'! %= 1,00 dm3

o!($a!$# d# ba(&"&dad d#l NH3 Kb= 1,80105

o!($a!$# d# lo( a(#( &d#al#( *= 0,0820 a$mdm3mol11

%od"$o &'!&"o d#l aa K= [H+][OH] = 1,00 1014

Incgnitas

o!"#!$%a"&'! d#l NH3#! la d&(ol"&'! [NH3]#

o!"#!$%a"&'! d# NH4+ OH#! la d&(ol"&'! [NH4+]#, [OH]#


9/37


Incgnitas

pH d# la d&(ol"&'! %#(l$a!$# pH

Otros smbolos

&(ol"&'! D


a!$&dad d# la (($a!"&a 7 n7)

o!"#!$%a"&'! d# la (($a!"&a 7 [7]

Ecuaciones

o!($a!$# d# ba(&"&dad d# la ba(# OH)baq) b+aq) + bOH aq) Kb=[+ b]

e[OH-]

e

b

[OH)b ]e

# #($ado d# lo( a(#( &d#al#( ( % + n * )

pH pH = lo[H+]

%od"$o &'!&"o d#l aa pH + pOH = 14

Solucin:

a) Lpo!!do "ompo%$am!$o &d#al pa%a #l a( amo!*a"o

n (NH3)=

( %

*)=

1,00 [a$m] &11,2[dm3 ]

0,0820 [a$mdm3 mol1 1]& 298[]=0,458mol NH

3,)

@a "o!"#!$%a"&'! d# la d&(ol"&'! (#%:

[NH3 ]=n(NH

3)

%D=

0,458 [mol NH3]

1,00 [dm3D ] =

0,458mol NH3

dm3D

=0,458mol /dm3

P#!!do #! "#!$a # #l amo!*a"o #( !a ba(# db&l, (# d&(o"&a%: #! aa (#! la #"a"&'!NH3aq) + H2O NH 4+ aq) + OHaq)

o!"#!$%a"&'! NH3 NH4+ OH

[ ]0 &!&"&al 0,458 0 0 mol/dm3


[ ]# #! #l #&l&b%&o 0,458 x x x mol/dm3

@a "o!($a!$# d# #&l&b%&oKb#(

Kb=[NH4

+]e[OH-]e

[NH3]e=

x & x

0,458x

=1,80105

L&, #! p%&m#%a ap%o>&ma"&'!, "o!(&d#%amo( d#(p%#"&abl#xD%#!$# a 0,458, la #"a"&'! (# %#d"# a

x=0,458 &1,80105=2,8C10

3mol/dm

3

#, "ompa%ada "o! 0,458 #( d#(p%#"&abl#?

#%%o% = 2,8C103mol/dm3/ 0,458 mol/dm3= 0,006 = 0,6 .

0,458 x= 0,458 0,003 = 0,455

[NH3]#= 0,455 mol NH3/ dm3D

b)

[NH4+]#=x= 2,8C103mol NH4+/ dm3

[OH]#=x= 2,8C103mol OH/ dm3


10/37


") G!# (# p#d# "al"la% la [H+] a pa%$&% d#l #&l&b%&o d# &o!&a"&'! d#l aa

H2O H+a)+ OHa)K= [H+][OH] = 1,00 1014

%#(l$a m:( (#!"&llo "al"la% #l pH d# la %#la"&'!

p= pH + pOH = 14

# (# ob$!# d# la a!$#%&o% (&! m:( # apl&"a% loa%&$mo( (a% la( d#D&!&"&o!#( d# pH pOH?

pOH = lo[OH] = lo2,8C103) = 2,54

pH = 14 2,54 = 11,46

Anlisis: Este pH es consistente con lo esperado. Si el amonaco fuese una base fuerte, el pH de una disolu-cin ,/ mol0dm1sera pH 23 4 lo ,/ 21,1. !na base d"bil tendr un pH menos bsico, ms prxi-mo a $.

. Se disuel2en *$ d&de 4&g,% edidos a 1$ JC * a" *$*%= KPa, de #esin% en una can"idadde a>ua su5icien"e a#a alcan(a# )%7 d&de disolucin. Calcule9a, El >#ado de disociacin del aon!aco en la disolucin.

-, El 4 de dic6a disolucin.Da"os9 R $%$* a"d&01ol01 %&1 N01ol01 K-4&, 1%81$07 (P.A.U. Jun. 10)Rta.:a) = 0,68. ; b) pH = 11,42


a( Aolm#! %= 20,0 dm3= 0,0200 m3NH3

p%#(&'! (= 202,6 a = 2,026105a

$#mp#%a$%a )= 10 0 = 283

Jolm#! d# la d&(ol"&'! %= 4,50 dm3

o!($a!$# d# ba(&"&dad d#l NH3 Kb= 1,C8105

o!($a!$# d# lo( a(#( &d#al#( *= 8,31 Qmol11

%od"$o &'!&"o d#l aa K= [H+][OH] = 1,00 1014

Incgnitas



Otros smbolos

&(ol"&'! D


a!$&dad d# la (($a!"&a 7 n7)o!"#!$%a"&'! d# la (($a!"&a 7 [7]

Ecuaciones

o!($a!$# d# ba(&"&dad d# la ba(# OH)baq) K b+aq) + bOH aq) Kb=[+ b]

e[OH- ]

e

b

[OH)b ]e

# #($ado d# lo( a(#( &d#al#( ( % + n * )

pH pH = lo[H+]

%od"$o &'!&"o d#l aa pH + pOH = 14,00

Solucin:

a) Lpo!!do "ompo%$am!$o &d#al pa%a #l a( amo!*a"o


11/37


n NH3=( %

* )=

2,026105[/a]& 0,0200[m3]

8,31 [Qmol1 1]& 283[]=1,C2mol NH3 ,)

@a "o!"#!$%a"&'! d# la d&(ol"&'! (#%:

[NH3 ]=n(NH3 )

%D=

1,C2[molNH3]

4,50[dm3D ] =0,382mol /dm3

omo #l amo!*a"o #( !a ba(# db&l, (# d&(o"&a%: #! aa (#! a #"a"&'!


o!"#!$%a"&'! NH3 NH4+ OH

[ ]0 &!&"&al 0,382 0 0 mol/dm3


[ ]# #! #l #&l&b%&o 0,382 x x x mol/dm3

@a "o!($a!$# d# #&l&b%&oKb#(

Kb

=[NH

4

+]e[OH-]

e

[NH3]e=

x & x

0,382x =1,C8105

L&, #! p%&m#%a ap%o>&ma"&'!, "o!(&d#%amo( d#(p%#"&abl#xD%#!$# a 0,382, la #"a"&'! (# %#d"# a

x=0,382& 1,C8105=2,6110

3 mol/dm3

#, "ompa%ada "o! 0,382 #( d#(p%#"&abl#?


12/37



P#mp#%a$%a )= 25 0 = 298

o!"#!$%a"&'! d# :"&do #$a!o&"o [H3OOH]0= 0,101 mol/dm3

%ado d# d&(o"&a"&'! d#l :"&do #$a!o&"o = 0,990. = 9,90103

Incgnitas


o!($a!$# d# a"&d# a

Otros smbolos


a!$&dad d# (($a!"&a d&(o"&ada nd

Ecuaciones

o!($a!$# d# a"&d# d#l :"&do HaG aq) aH+aq) + Gaaq) Ka=[H+]e

a [Ga -]e[Ha G ]e

pH pH = lo[H+]pOH pOH = lo[OH]

%od"$o &'!&"o d#l aa pH + pOH = 14

%ado d# d&(o"&a"&'! = nd/ n0

Solucin:

a) L# a! d&(o"&ado

[H3OOH]d= [H3OOH]0=

= 9,90103molH3 OOH d&(?

mol H3OOH &!&"?0,101

mol H3 OOH &!&"?

1dm3d&(ol"&'!

=1,00103mol H3 OOH d&(?

dm3d&(ol"&'!

P#!!do #! "#!$a # #l :"&do #$a!o&"o #( ! :"&do db&l, (# d&(o"&a%: #! aa (#! la #"a"&'!

H3OOHaq) H+aq) + H3OOaq)

o!"#!$%a"&'! H3OOH H+ H3OO

[ ]0 &!&"&al 0,101 0 0 mol/dm3

[ ]d d&(o"&ada o Do%mada 1,00103 K 1,00103 1,00103 mol/dm3

[ ]# #! #l #&l&b%&o 0,101 1,00103= 0,100 1,00103 1,00103 mol/dm3

pH = lo[H+] = lo1,00103) = 3,00

b) @a "o!($a!$# d# #&l&b%&oKa#(

Ka=[H3OO

-]e[H+]e

[H3OOH]e=

1,00103 &1,00103

0,100 =1,00105

1$. Una disolucin de C4&;COO4 de concen"#acin $%* ol/d&es"' ioni(ada al $%@7 +. Calcula9a, Las concen"#aciones de C4&;COO4 de 4&Oen el e3uili-#io.-, La cons"an"e de ioni(acin del 'cido.

(P.A.U. Set. 99)Rta.:a) [H3 OOH]#B 0,2 mol/dm3; [H3O+]#= 1,9103mol/dm3; b)Ka=1,8105


13/37



o!"#!$%a"&'! d# la d&(ol"&'! d# :"&do #$a!o&"o [H3OOH]0= 0,200 mol/dm3

%ado d# d&(o"&a"&'! d#l :"&do #$a!o&"o = 0,950. = 9,50103

Incgnitas

o!"#!$%a"&'! d# H3OOH #! #l #&l&b%&o [H3OOH] #

o!"#!$%a"&'! d# H3O+#! #l #&l&b%&o [H3O+]#

o!($a!$# d# a"&d# a

Otros smbolos



Ecuaciones


a [Ga -]e[Ha G ]e

pH pH = lo[H+]pOH pOH = lo[OH]

%od"$o &'!&"o d#l aa pH + pOH = 14

%ado d# d&(o"&a"&'! = nd/ n0

Solucin:

a) L# a! d&(o"&ado

[H3OOH]d= [H3OOH]0=

=9,50103 molH3 OOH d&(?molH3 OOH&!&"?

0,200 molH3 OOH&!&"?dm3 d&(ol"&'!

=1,90103 molH3 OOHd&(?dm3 d&(ol"&'!



o!"#!$%a"&'! H3OOH H+ H3OO

[ ]0 &!&"&al 0,200 0 0 mol/dm3


[ ]# #! #l #&l&b%&o 0,200 1,90103= 0,198 1,90103 1,90103 mol/dm3

[H3OOH]#= 0,198 mol/dm3

[H3O+]#= [H+]#= 1,90103mol/dm3

b) @a "o!($a!$# d# #&l&b%&oKa#(

Ka=[H3OO

-]#[H+]#

[H3OOH ]#=

1,90103 &1,90103

0,198 =1,8210

5

11. Se #ea#a una disolucin de un 'cido ono#"ico d?-il de 5#ula 4A% de la si>uien"e ane#a9$%1$ oles del 'cido en *7$ c&de a>ua. Si es"a disolucin se ioni(a al 1%7+% calcule9

a, La cons"an"e de ioni(acin del 'cido.-, El 4 de la disolucin.

(P.A.U. Set. 06)

Rta. a)Ka= 9,1105; b) pH = 2,2


14/37



a!$&dad mol#() d# :"&do mo!op%'$&"o nHG)0= 0,100 mol/dm3

Jolm#! d# la d&(ol"&'! %= 250 "m3= 0,250 dm3

%ado d# d&(o"&a"&'! d#l :"&do = 1,50. = 1,50102

Incgnitas

o!($a!$# d# &o!&a"&'! d#l :"&do Ka


Otros smbolos



Ecuaciones


e

a [Ga-]e

[Ha G ]epH pH = lo[H+]

pOH pOH = lo[OH]

%od"$o &'!&"o d#l aa pH + pOH = 14

%ado d# d&(o"&a"&'! = nd/ n0

Solucin:

a) @a "o!"#!$%a"&'! mola% &!&"&al d#l :"&do #(, (po!!do # #l Aolm#! d# d&(ol"&'! #( #l m&(mo # #ld# aa

[HG ]0=0,100 mol HG

0,250dm3 =0,400 mol GH /dm3D

L# a! d&(o"&ado

ndGH) = n0GH) = 1,50102[mol HG d&(o"&ado( / mol HG &!&"&al#(] 0,100 [mol HG &!&"&al#(] == 1,50103mol HG d&(o"&ado(

"o! !a "o!"#!$%a"&'!

[HG ]d=1,50103 molHG

0,250dm3 =6,00103 mol/dm3

@a #"a"&'! #(

HGaq) H +aq) + Gaq)

o!"#!$%a"&'! H3OOH H+ H3OO

[ ]0 &!&"&al 0,400 0 0 mol/dm3


[ ]# #! #l #&l&b%&o 0,400 6,00103= 0,396 6,00103 6,00103 mol/dm3

@a "o!($a!$# d# #&l&b%&oKa#(

Ka=[G-]e[H

+]e

[HG ]e=

6,00103 & 6,00103

0,394 =9,14105

b) pH = lo[H+] = lo6,00103) = 2,22


15/37


1*. A *7 $C el >#ado de disociacin de una disolucin de concen"#acin $%* ol/d&de 'cido ac?"ico:'cido e"anoico< 2ale $%$$@7. Calcule9a, La concen"#acin de iones ace"a"o :iones e"anoa"oeniones e iones 6id#oilo en el

e3uili-#io.-, El 4.c, La cons"an"e de disociacin del 'cido ac?"ico.

(P.A.U. Set. 05)

Rta.:a) [H

+

]#= [H3OO

]#= 1,9103

mol/dm3

; [OH

]#= 5,31012

mol/dm3

; b) pH = 2,C;")Ka= 2,0105


P#mp#%a$%a )= 25 0 = 298

o!"#!$%a"&'! d# :"&do #$a!o&"o [H3OOH]0= 0,20 mol/dm3

%ado d# d&(o"&a"&'! d#l :"&do #$a!o&"o = 0,0095 = 9,5103

Incgnitas

o!"#!$%a"&o!#( d# lo( &o!#( [H3OO], [H+], [OH]

pH d# la d&(ol"&'! pHo!($a!$# d# a"&d# Ka

Otros smbolos



Ecuaciones


a [Ga-]e[Ha G]e

pH pH = lo[H+]

pOH pOH = lo[OH]

%od"$o &'!&"o d#l aa H2O l) H+aq) + OHaq) pH + pOH = 14

%ado d# d&(o"&a"&'! = nd/ n0

Solucin:

a) b) L# a! d&(o"&ado

[H3OOH]d= [H3OOH]0=

= 9,5103mol H3OOH d&(?

molH3 OOH &!&"?0,20

mol H3 OOH&!&"?

dm3d&(ol"&'! =1,910

3mol H3 OOH d&(?

dm3d&(ol"&'!



o!"#!$%a"&'! H3OOH H+ H3OO

[ ]0 &!&"&al 0,20 0 0 mol/dm3

[ ]d d&(o"&ada o Do%mada 2,0103 2,0103 2,0103 mol/dm3

[ ]# #! #l #&l&b%&o 0,20 2,0103= 0,20 2,0103 2,0103 mol/dm3

@a( "o!"#!$%a"&o!#( d# &o!#( a"#$a$o # &d%o#!&o!#( (# (a"a! #! la $abla[H3OO] = 2,0103mol/dm3


16/37


[H+] = 2,0103mol/dm3

@a "o!"#!$%a"&'! d# &o!#( &d%'>&do (# d#d"#! d# la "o!($a!$# d#l p%od"$o &'!&"o d#l aa

pH + pOH = 14

%&m#%o (# "al"la #l pH

pH = lo[H+] = lo2,0103) = 2,C2

pOH = 14,00 2,C2 = 11,28

[OH] = 10pOH= 1011,28= 5,31012mol/dm3

") @a "o!($a!$# d# #&l&b%&oKa#(

Ka=[H3OO

-]e[H +]

e

[H3OOH]e=

2,0103 & 2,0103

0,20 =2,0105

Anlisis: Si se usasen ms cifras sinificati6as, el 6alor de la constante sera 1,8210-5ms parecido al 6a-lor tabulado.

1&. Dado un 'cido d?-il ono#"ico de concen"#acin $%$1 ol/d& sa-iendo 3ue se ioni(a en un1&+% calcula#9a, La cons"an"e de ioni(acin.-, El 4 de la disolucin.c, FGu? 2oluen de disolucin de concen"#acin $%$* ol/d&de 6id#ido de sodio se#'n nece0

sa#ios a#a neu"#ali(a# cole"aen"e 1$ c&de la disolucin del 'cido an"e#io#H(P.A.U. Jun. 04)

Rta.:a)Ka=1,9104; b) pH = 2,9; ") %= 5 "m3DNaOH


o!"#!$%a"&'! d# :"&do db&l mo!op%'$&"o HG [HG]0= 0,0100 mol/dm3

%ado d# &o!&a"&'! d#l :"&do = 13,0. = 0,130

o!"#!$%a"&'! d#l &d%'>&do d# (od&o [NaOH] = 0,0200 mol/dm3

Jolm#! d# :"&do # (# d#b# !#$%al&a% %a= 10,0 "m3

Incgnitas


o!($a!$# d# a"&d# a

Jolm#! d# NaOH # !#$%al&a! 10 "m3d# la d&(ol"&'! d#l :"&do J

Otros smbolos

o!"#!$%a"&'! mol/dm3) d# :"&do db&l # (# d&(o"&a xa!$&dad d# :"&do d&(o"&ado nd

Ecuaciones

o!($a!$# d# a"&d# d#l :"&do mo!op%'$&"o HG aq) H+aq) + Gaq) Ka=[H+]e

a [Ga- ]e[Ha G ]e

pH pH = lo[H+]

pOH pOH = lo[OH]

%od"$o &'!&"o d#l aa pH + pOH = 14

%ado d# d&(o"&a"&'! = nd/ n0

Solucin:


17/37


a) L# a! d&(o"&ado

[HG ]d=[HG]0=0,130mol HGd&(o"&ado(

molHG &!&"&al#( 0,0100

mol HG&!&"&al#(

dm3d&(ol"&'!

=1,30103mol HG d&(o"&ado(

dm3d&(ol"&'!

R! :"&do db&l mo!op%'$&"o (# d&(o"&a%: #! aa (#! la #"a"&'!

HGaq) H+aq) + Gaq)

o!"#!$%a"&'! HG H+ G

[ ]0 &!&"&al 0,0100 0 0 mol/dm3

[ ]d d&(o"&ada o Do%mada 1,30103 1,30103 1,30103 mol/dm3

[ ]# #! #l #&l&b%&o 0,0100 1,30103= 0,008C 1,30103 1,30103 mol/dm3

@a "o!($a!$# d# #&l&b%&oKa#(

Ka=[G-]e[H

+]e[HG ]e

=1,30103 &1,30103

0,008C =1,9104

b) pH = lo[H+] = lo1,30103) = 2,89

") @a %#a""&'! d# !#$%al&a"&'! #!$%# #l :"&do mo!op%'$&"o HG #l &d%'>&do d# (od&o NaOH #(

HG aq) + NaOH aq) K NaG aq) + H2O aq)


18/37


a) omo

pH = lo[H+]

2,0 = lo[H+]

[H+] = 102,0= 1102mol/dm3= 0,01 mol/dm3

b) @a "o!"#!$%a"&'! &!&"&al a!$#( d# d&(o"&a%(#) d# :"&do a"$&"o #(

[H3OOH ]0=n (H3 OOH)

% =

0,30molH3OOH

0,050dm3D =6,0 molH3 OOH /dm

3D

# la #($#&om#$%*a d# la %#a""&'! d# d&(o"&a"&'!


(# d#d"# # la "o!"#!$%a"&'! d# :"&do a"$&"o d&(o"&ado [H3OOH]d#( la m&(ma # la d# &o!#( &d%'-#!o p%od"&do( [H+]# la d# &o!#( a"#$a$o [H3OO]#

[H3OOH]d= [H+]#= [H3OO]#= 0,01 mol/dm3

/c& &+ de #i3ue0(a en eso se diluen con a>ua des"ilada 6as"a 1$$ c&. Calcula9a, El 4 de la disolucin #esul"an"e de e(cla# 7$ c&del 'cido clo#6!d#ico #ea#ado an"e#io#0

en"e con 7$ c&de 6id#ido de sodio de concen"#acin $%1 ol/d&.-, El 4 de la disolucin #esul"an"e de e(cla# los o"#os 7$ c&% del 'cido clo#6!d#ico #ea#ado

con *7 c&de 6id#ido de sodio de concen"#acin $%1 ol/d&.(P.A.U. Set. 99)

Rta.:a) pH =C; b) pH = 1,48


&(ol"&'! "om#%"&al d# Hl Aolm#! %"= 0,C3 "m3

d#!(&dad 7= 1,35 /"m3

%a r= 3C. = 0,3C

Jolm#! p%#pa%ado d# d&(ol"&'! d&l&da d# Hl %d= 100 "m3= 0,100 dm3

Jolm#! # (# m#"la d# d&(ol"&'! d&l&da d# Hl %a= 50 "m3= 50103dm3

Jolm#! # (# m#"la d# d&(ol"&'! d# NaOH %b= 50 "m3= 50103dm3

o!"#!$%a"&'! d# la d&(ol"&'! d# NaOH [NaOH] = 0,10 mol/dm3

Ia(a mola% d#l :"&do "lo%*d%&"o 8Hl) = 36,5 /mol


19/37


Incgnitas

pH d# la m#"la 50/50 pH1

pH d# la m#"la 50/25 pH2

Ecuaciones

pH pH = lo[H+]

%od"$o &'!&"o d#l aa pH + pOH = 14

Solucin:

a) L# "al"la a!$#( la "o!"#!$%a"&'! d# lo( 100 "m3d# d&(ol"&'! d&l&da? @a "a!$&dad d# (ol$o d&(#l$o #! lad&(ol"&'! d# pa%$&da #(

n=0,C3["m3D ]1,35[ D ]

1 ["m3D ]3C[ Hl ]100[ D ]

1[mol Hl]36,5[ Hl ]

=1,0102 mol Hl #! la d&(ol"&'! d# pa%$&da

[Hl] = 1,010

2

mol Hl / 100 "m

3

D= 0,10 mol/dm

3

L# pla!$#a la %#a""&'! #!$%# #l Hl #l NaOH pa%a A#% %#a"$&Ao #($: #! #>"#(o, A!do #, !a A# a($a-da la #"a"&'!, #l Hl #l NaOH %#a""&o!a! mol a mol?

%P= 50 "m3 Hl + 50 "m3 NaOH = 100 "m3= 0,100 dm3d# m#"la?

Hl NaOH K Na+ l H2O

n0 a!$&dad &!&"&al 5,0103 5,0103 0 0 mol

n% a!$&dad # %#a""&o!a o (# Do%ma 5,0103 5,0103 5,0103 5,0103 5,0103 mol

nD a!$&dad al D&!al d# la %#a""&'! S 2104 S 2104 5,0103 5,0103 mol

[ ]D o!"#!$%a"&'! D&!al S 2103 S 2103 5,0102 5,0102 mol/dm3

No (# p#d# d#"&d&% (($a!"&a #! "a!$&dad #da (&! %#a""&o!a%, p#( la p%#"&(&'! d# la( m#d&da( !op#%m&$#! a"#%lo?

@a d&D#%#!"&a #!$%# la "a!$&dad d# Hl la d# NaOH #($: D#%a d# la p%#"&(&'! d# la m#d&da o%&&!al, , #! "o!-(#"#!"&a, ('lo (# pod%*a d#"&% # la d&(ol"&'! %#(l$a!$# (#%: :"&da, !#$%a o b:(&"a, #( d#"&% # $#!d%: ! pH"omp%#!d&do #!$%# 2,C 11,3?


20/37


[Hl] = 2,5103mol Hl / 0,0C5 dm3D= 3,3102mol/dm3

ada #eaccionan en"#e s! dando una disolucin neu"#a.-, Un 'cido su -ase conu>ada se di5e#encian en un #o"n. Pon un eelo.

c, La -ase conu>ada de un 'cido 5ue#"e es una -ase 5ue#"e. Pon un eelo.(P.A.U. Set. 98)

Rta.:a) E; b) J; ") E?

Solucin:

a) Eal(o? @a ba(# "o!ada d# ! :"&do #( la #(p#" #! la # (# "o!A%$# "a!do "#d# ! p%o$'!?

Hl + H2O l+ H3O+

T"&do a(# "o!ada

R!a %#a""&'! #!$%# ! :"&do ( ba(# "o!ada, !o (#%*a !a %#a""&'!, a # la( #(p#"( D&!al#( (o! la(m&(ma( # la( &!&"&al#(

Hl + ll+ Hl

b) J#%dad#%o? J#% #l apa%$ado a!$#%&o%?

") Eal(o? o!&o H3O+?


21/37


T"&do W W W

a(# W W

O32aq) + H2O l) HO3aq) + OHaq)

HO42aq) + H2O l) O43aq) + H3O+aq)

HO42aq) + H2O l) H2O4aq) + OHaq)

NH4+aq) + H2O l) NH3aq) + H3O+aq)

@a %#a""&'! :"&do-ba(# d#l &'! o>o!&o H3O+) (#%*a la "#(&'! d#l &'! &d%'#!o H+a o$%a mol"la d# aa,p#%o "omo lo( p%od"$o( d# la %#a""&'! (o! lo( m&(mo( # lo( %#a"$&Ao(, !o #( !a %#a""&'! *m&"a !ada"amb&a?

&.a, Esc#i-a las #eacciones de disociacin en a>ua% se>n el odelo de B#Tns"ed0Lo#% de las si0

>uien"es esecies 3u!icas9 C4&COO4 4& 4) C;

-, Indi3ue los a#es 'cido/-ase conu>ados.(P.A.U. Jun. 11)

Solucin:a)

H3OOH aq) + H2O l) H3OOaq) + H3O+aq)

NH3aq) + H2O l) NH4+aq) + OHaq)

NH4+aq) + H2O l) NH3aq) + H3O+aq)

Naq) + H2O l) HN aq) + OHaq)

H3OOH H3OOH H3OO

H2O H3O+

NH3 H2O OH NH3 NH4+

NH4+ NH4+ NH3 H2O H3O+

N H2O OH N HN

). Cole"a los si>uien"es e3uili-#ios 'cido0-ase de B#Tns"ed0Lo#% ca#ac"e#i(ando los co##es0ondien"es a#es 'cido0-ase conu>ado9a, . . . . . 4*O CO &*0 4&O

-, 4) O4;4*O . . . . .c, . . . . . 4*O 4 &O SO)*;

(P.A.U. Set. 01)Rta.:a) HO3; b) NH3; ") HLO4

Solucin:


22/37


a) HO3 O32ba(# "o!ada d#l :"&do HO3? H3O+:"&do "o!ado d# la ba(# H2O

b) NH3 NH3ba(# "o!ada d#l :"&do NH4+? H2O :"&do "o!ado d# la ba(# OH

") HLO4 LO42ba(# "o!ada d#l :"&do HLO4? H3O+:"&do "o!ado d# la ba(# H2O

7. Cole"e las si>uien"es #eacciones 'cido0-ase e iden"i5i3ue los a#es conu>ados 'cido0-ase9a, 4Cl aq, O4;aq! c, 4O&aq, 4*O l, -, CO&*;aq! 4*O l, d, 4&aq, 4*O l,

(P.A.U. Set. 13)

Rta.:a) Hl aq) + OHaq) l aq) + H2O l); b) O32aq) + H2O l) HO 3aq) + OHaq);") HNO3aq) + H2O l) NO3aq) + H3O+aq); d) NH3aq) + H2O l) NH 4+aq) + OHaq)

Solucin:

a) Hl aq) + OHaq) l aq) + H2O l)


23/37


") uales.-, El 4 de la disolucin es 1.(P.A.U. Jun. 12)

Solucin:

a) Gp%o>&madam#!$# "o%%#"$a? a!do ! :"&do HG db&l (# d&(#lA# #! aa, (# &o!&a pa%"&alm#!$# #! &o-!#( G H+? o!&o $amb&! 0,1 mol/dm3, al #($a% $o$alm#!$# d&(o"&ado,

HG + H2O K G+ H3O+

po% lo # #l pH (#%*a 1pH = -lo[H+] = -lo[H3O+] = -lo 0,1 = 1

#%o ! :"&do db&l #($: pa%"&alm#!$# &o!&ado, la "o!"#!$%a"&'! d# &o!#( o>o!&o (#%*a m#!o% # 0,1mol/dm3, #l pH mao% # 1?

o!"#!$%a"&'! HG H3O+ G

[ ]0 &!&"&al 0,1 B 0 0 mol/dm3


[ ]# #! #l #&l&b%&o 0,1 x x x mol/dm3

L& la "o!($a!$# d# a"&d# d#l :"&do db&l #( Ka, la "o!"#!$%a"&'!x d# &o!#( o>o!&o #! #l #&l&b%&o (# ob$!#

Ka=[G-]

e[H+]

e

[HG ]e=

x & x

0,1x=

x2

0,1x

L& la "o!"#!$%a"&'!xd# :"&do db&l d&(o"&ado D#(# d#(p%#"&abl# D%#!$# a la "o!"#!$%a"&'! 0,1 mol/dm 3,

xKa &0,1

R! Aalo% d# la "o!($a!$# d# a"&d# "omo la d#l :"&do a"$&"o,KaB 10-5da%*a !a "o!"#!$%a"&'!

xB 10-3

! pH B 3

. Pa#a una disolucin acuosa de un 'cido 4A de Ka 181$07% us"i5i3ue si son 2e#dade#as o 5alsaslas si>uien"es a5i#aciones9a, La cons"an"e de acide( de 4A es eno# 3ue la cons"an"e de -asicidad de su -ase conu>ada.


24/37


-, Si se dilue la disolucin del 'cido% su >#ado de disociacin e#anece cons"an"e.(P.A.U. Set. 12)

Solucin:

a) Eal(a? a!do ! :"&do HG db&l (# d&(#lA# #! aa, (# &o!&a pa%"&alm#!$# #! &o!#( G H+? p%#(a% po%

G+ H2O HG + OH

@a "o!($a!$# d# ba(&"&dad d# #($a ba(# #(

Kb=[HG ]e[OH- ]e

[G-]e

L& ml$&pl&"amo( amba( "o!($a!$#(, ob$#!#mo(

Ka & Kb=[G-]e[H

+]e[HG ]e

&[HG]e [OH

-]e[G-]e

=[H+]e & [OH-]e=K

la "o!($a!$# d# &o!&a"&'! d#l aa # Aal#K= 110-14? omo la "o!($a!$# d# a"&d# d#l :"&do Aal# 110 -5, lad# ( ba(# "o!ada Aal#

Kb=K

Ka=

11014

1105=1109


25/37


x 91105

& 0,025=5104 mol/dm30,025mol/dm3

#l !#Ao %ado d# d&(o"&a"&'! (#%*a

9=5104

0,025=0,05=5.

a!$o m:( d&l&da #( la d&(ol"&'!, mao% #( #l %ado d# d&(o"&a"&'!?

L& llamamo( c0a la "o!"#!$%a"&'! d# la d&(ol"&'! d# :"&do HG, la "o!"#!$%a"&'! cd# :"&do d&(o"&ado (# p#d##>p%#(a% #! D!"&'! d# %ado d# d&(o"&a"&'! "omo, c= "#(o d# &o!#( o>o!&o, lo # "o!D%# a la d&(ol"&'! ! "a%:"$#% :"&do?


26/37


Na+a)+ H2O NaOHa)+ H3O+a)

#($: $o$alm#!$# d#(plaado a"&a la &%da? No (# &d%ol&a?#%o #l &o! &pob%om&$o p%oA!# d# ! :"&do db&l #l :"&do &pob%omo(o), (# &d%ol&a

%Oa)+ H2O OHa)+ H%Oa)

eno< clo#u#ode o"asio. Wo#ule las ecuaciones inicas 3ue us"i5i3uen la #esues"a.

(P.A.U. Set. 06)

Rta.:HNO3^ l ^ NaH3OO

Solucin:

uien"es disoluciones acuosasde9a, Ace"a"o de sodio :e"anoa"o de sodio&do d# (od&o #( !a ba(# D#%$#, m!$%a( # #l amo!*a"o #( !a ba(# db&l a un eelo de una sal cua disolucin acuosa #esen"e un 4 'cido un eelo deuna sal cua disolucin acuosa sea neu"#a. Ra(one las #esues"as.

(P.A.U. Set. 02)

Rta.:a) L*; b) NH4l :"&do, Nal !#$%o

Solucin:

a) R!a (al, #l#"$%ol&$o D#%$#, "a!do (# d&(#lA# #! aa #da $o$alm#!$# d&(o"&ado #! (( &o!#(?


28/37


NH4++ H2O NH3+ H3O+

@a "o!"#!$%a"&'! d# &o!#( o>o!&o #! la d&(ol"&'! am#!$a #l pH d# la d&(ol"&'! (#%: :"&do?uien"es a5i#aciones es cie#"a o no9a, El ne#o de oles de 'cido de -ase 3ue #eacciona#on son i>uales.-, El 4 de la disolucin 5o#ada uede se# dis"in"o de .c, Los 2olenes de 'cido de -ase consuidos son i>uales.

(P.A.U. Jun. 99)

Rta.:a) E; b) J; ") E?

Solucin:

a) Eal(o? L&, po% ##mplo, #l :"&do #( (lD%&"o la ba(#, &d%'>&do d# (od&o, "a!do (# al"a!"# #l p!$o d##&Aal#!"&a, ab%:! %#a""&o!ado #l dobl# d# mol#( d# &d%'>&do d# (od&o # d# :"&do (lD%&"o

H2LO4+ 2 NaOH K Na2LO4+ 2 H2O

b) J#%dad#%o? L& #l :"&do #( db&l la ba(# D#%$#, #! #l p!$o d# #&Aal#!"&a ('lo #>&($&%: la (al, "o pH(#%: b:(&"o pH ^ C)?

H3 OOH + NaOH K NaH3 OO) + H2O


29/37


") Eal(o? L&, po% ##mplo, #l :"&do #( "lo%*d%&"o 1,00 mol/dm 3 la ba(# &d%'>&do d# (od&o 2,00 mol/dm3, #!#l p!$o d# #&Aal#!"&a ab%:! %#a""&o!ado lo( m&(mo( mol#( d# "lo%*d%&"o # d# &d%'>&do d# (od&o,

p#%o #l Aolm#! d# "lo%*d%&"o (#%: #l dobl# # #l d# d&(ol"&'! d# &d%'>&do d# (od&o?

17. De5ina -#e2een"e el conce"o de disolucin #e>ulado#a seXale en"#e los si>uien"es a#es desus"ancias% el o los 3ue 5o#a#'n una disolucin #e>ulado#a9

a, cido clo#6!d#ico / clo#u#o de sodio.-, cido cian6!d#ico / cianu#o de o"asio.c, cido n!"#ico :"#iooni"#a"oV, de 6id#>eno< / ni"#a"o de aonio :"#iooni"#a"oV, de aonio&do d# (o-d&o, mol a mol, la "a!$&dad d# "lo%*d%&"o # %#a""&o!a #( la m&(ma # la d#l &d%'>&do d# (od&o

Hl a)+ NaOH a)K Nala)+ H2O

[Hl ]=nHl

%DHl=

nNaOH%DHl

=%m[NaOH]

%D Hl=

%m &0,01000

0,01000dm3=%m mol Hl /dm

3D

do!d# %m#( #l Aolm#! m#d&o a($ado d# "lo%*d%&"o #! dm3?

7. Elica de"alladaen"e co se o-"end#!a en el la-o#a"o#io la concen"#acin de una disolucinde 'cido clo#6!d#ico de concen"#acin a#oiada 1 ol/d&% eleando una disolucin de 6id#0ido de sodio% de concen"#acin eac"a $%$1 ol/d&. o-#a el a"e#ial eleado la 5o#ade #eali(a# los c'lculos.

(P.A.U. Jun. 97)

Solucin:

%&m#%o (# d&l# "! A#"#( la d&(ol"&'! d# Hl? L# m&d#! "o! !a p&p#$a 10,00 "m 3d# la d&(ol"&'! d#Hl 1 mol/dm3 (# #"a! #! ! ma$%a aDo%ado d# 1000 "m3? L# aZad# aa a($a la ma%"a d#l aDo%o? L#$apa (# Aol$#a Aa%&a( A#"#( pa%a omo#!#&a%?L# ll#!a po% #!"&ma d#l "#%o !a b%#$a d# 25 "m3"o! la d&(ol"&'! d&l&da d# Hl (# ab%# la llaA# a($a

# la d&(ol"&'! al"a!"# #l "#%o?L# m&d#! "o! o$%a p&p#$a 10,00 "m3d# d&(ol"&'! d# NaOH? L# pa(a! a ! ma$%a #%l#!m##% (# l# aZad#!do( o$a( d# d&(ol"&'! d# D#!olD$al#*!a? @a d&(ol"&'! d#b# $oma% ! "olo% %o(a?L# "olo"a #l #%l#!m##% (ob%# ! pap#l bla!"o # %#(al$# #l "olo% %o(a d# la d&(ol"&'! (# "olo"a d#baod# la b%#$a # "o!$!# #l Hl? L# ab%# la llaA# d#a!do "a#% #l Hl #! #l #%l#!m##% #! "o%%o( (# a&$aa($a # #l "olo% %o(a d#(apa%#"a? L# a!o$a #l Aalo% d#l Aolm#! d# Hl a($ado?L# $&%a #l "o!$#!&do d#l #%l#!m##% (# laAa? L# A#lA#! a m#d&% "o! la p&p#$a 10,00 "m 3d#l NaOH (#A%$#! #! #l #%l#!m##%, aZad&!dol# do( o$a( d# D#!olD$al#*!a? L# A#lA# a ll#!a% la b%#$a "o! Hl d&l&-do (# po!# a "#%o?L# "olo"a #l #%l#!m##% bao la b%#$a (# ab%# la llaA# a($a ! "m 3m#!o( # #l Aolm#! a($ado la p%&-m#%a A#? L# a&$a #l #%l#!m##% (# d#a o$#a% #l "lo%*d%&"o, %#moA!do "o!$&!am#!$#, a($a # #l "o-lo% %o(a d#(apa%#"a? L# a!o$a #($# Aalo% "omo J1?

L# %#p&$# #l p%o"#(o o$%a( do( A#"#( $oma!do Aolm#!#( J 2 J3? L& lo( $%#( Aalo%#( (o! lo (D&"!$#m#!$#p%'>&mo( `0,2 "m3) (# alla #l Aalo% m#d&o? L& !o, (# d#(p%#"&a #l m:( al#ado (# $oma la m#d&a d# lo(o$%o( do(? %m?@a "o!"#!$%a"&'! d#l Hl d&l&do (# "al"la po% #($#&om#$%*a? Gl %#a""&o!a% #l "lo%*d%&"o "o! #l &d%'>&-do d# (od&o, mol a mol, la "a!$&dad d# "lo%*d%&"o # %#a""&o!a #( la m&(ma # la d#l &d%'>&do d# (od&o

Hl a)+ NaOH a)K Nala)+ H2O

[Hl ]d&l=nHl

%D Hl=

nNaOH%D Hl

=%m[NaOH ]

%D Hl=

%m &0,01000

0,01000dm3=%m molHl /dm

3D

do!d# %m#( #l Aolm#! m#d&o a($ado d# "lo%*d%&"o #! dm3?

omo #l "lo%*d%&"o o%&&!al (# d&l' 100 A#"#(, la "o!"#!$%a"&'! d#l "lo%*d%&"o c1 mol/dm

3

(#%:[Hl]1= 100 %m) mol Hl / dm3D


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=. En el la-o#a"o#io se #eali(a la 2alo#acin de 7$%$ c&de una disolucin de aO4 se >as"a#on*$%$ c&de 4Cl de concen"#acin $%1$ ol/d&

a, Di-ue el on"ae ee#ien"al indicando en el iso las su-s"ancias el no-#e del a"e0#ial eleado.

-, Esc#i-a la #eaccin 3u!ica 3ue "iene lu>a# calcule la concen"#acin ola#idad de la -ase.(P.A.U. Set. 09)

Rta.:b) [NaOH] = 0,040 mol/dm3

Solucin:

a) L# m&d#! "o! !a p&p#$a d# 20 "m3, 20 "m3d# la d&(ol"&'!d# NaOH (# Aa"*a! #! ! ma$%a #%l#!m##% d# 250 "m3? L#l# #"a! do( o$a( d# d&(ol"&'! d# D#!olD$al#*!a?L# ll#!a la b%#$a d# 50 "m3"o! la d&(ol"&'! d# Hl po% #!"&-ma d#l 0 (# ab%# la llaA# a($a # #l p&"o d# la b%#$a #d#ll#!o #l !&A#l d#l Hl #($ #! 0?

b) Hl aq) + NaOH aq) K Nal aq) + H2O l)

:l"lo(@a mola%&dad !omb%# d#(a"o!(#ado po% la XRG) #( la "o!-"#!$%a"&'! d#l (ol$o #! mol/dm3?

a!$&dad d# HlnHl) = 2010-3dm3D 0,10 mol Hl / dm3D= 2,010-3mol Hl

ada mol d# Hl %#a""&o!a "o! ! mol d# NaOH, po% lo # la "a!$&dad d# NaOH "o!$#!&da #! lo( 50 "m 3d#d&(ol"&'! #( la m&(ma, la "o!"#!$%a"&'! d# NaOH #(

[NaOH]=2,0103 mol NaOH

50103 dm3 =0,040mol NaOH/dm3

. En la 2alo#acin de *$%$ L de una disolucin de 'cido clo#6!d#ico se 6an >as"ado 1%1 L deuna disolucin de 6id#ido de sodio de concen"#acin $%1*7 ol/d&.a, Calcule la concen"#acin de la disolucin del 'cido indicando la #eaccin 3ue "iene lu>a#.-, Indi3ue el a"e#ial #eac"i2os necesa#ios% as! coo el #ocediien"o a#a lle2a# a ca-o la 2alo0

#acin.(P.A.U. Set. 13)

Rta.: a) [Hl] = 0,0013 mol/dm3

Solucin:

a) @a %#a""&'! a($ada #(Hl aq) + NaOH aq) K Nal aq) + H2O l)

:l"lo( L& (# a! a($ado 18,1 m@ d# d&(ol"&'! d# &d%'>&do d# (od&o d# "o!"#!$%a"&'! 0,125 mol/dm3la"a!$&dad d# &d%'>&do d# (od&o # %#a""&o!a #(

n (NaOH)=18,1"m3DNaOH0,125mol NaOH

1000"m3DNaOH=2,26103 mol NaOH

@a "a!$&dad d# :"&do "lo%*d%&"o # %#a""&o!a #(

n (Hl)=2,26103 mol NaOH1molHl

1 mol NaOH=2,26103 mol Hl

la "o!"#!$%a"&'! d# la d&(ol"&'! d# Hl #(

[Hl ]=2,26103 mol Hl

20,0"m3 D Hl

103 "m3

1,00dm3=0,113 mol Hl/dm3D

50

40

30

20

10

0

"u#$%a&$ 50 m'c() *C+

$#+$)m$,$#

&$ 250 m'c() 50 m' &$ -aO*, &(. /(%a. &$$)(+%a+$)a


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%o"#d&m!$o d# Aalo%a"&'! o! !a p&p#$a d# 20 "m3(# m&d#! 20,0 "m3d# d&(ol"&'! d# Hl (# A%$#!#! ! ma$%a #%l#!m##% d# 100 "m3? L# aZad#! do( o$a( d# al d# b%omo$&mol la d&(ol"&'! (# AolA#%: d#"olo% ama%&llo? L# ll#!a !a b%#$a d# 25 "m3"o! d&(ol"&'! d# NaOH d# "o!"#!$%a"&'! 0,125 mol/dm3po% #!-"&ma d#l "#%o? L# ab%# la llaA# a($a # #l p&"o d# la b%#$a #($ ll#!o #l !&A#l #! "#%o? L# d#a! "a#% 1C "m 3

(ob%# #l #%l#!m##% (# a&$a? L# ab%# la llaA# d# la b%#$a pa%a d#a% "a#% la d&(ol"&'! d# NaOH #! p##Zo("o%%o( m!$%a( (# &mp%&m# ! moA&m!$o "&%"la% al #%l#!m##% a($a # #l "olo% d#l "o!$#!&do d#l #%l#!-m##% pa(# a al? L# a!o$a #l Aolm#! d# NaOH a($ado p? #? 18,5 "m 3) (# $&%a #l "o!$#!&do d#l #%l#!m##%

(# laAa #l ma$%a? L# A#lA# a ll#!a% la b%#$a "o! NaOH a($a #l "#%o? L# m&d#! o$%o( 20 "m 3d# Hl "o! lap&p#$a, (# A%$#! #! #l #%l#!m##% laAado p#%o !o !#"#(a%&am#!$# (#"o) (# aZad#! do( o$a( d# al d# b%o-mo$&mol? L# "olo"a #l #%l#!m##% bao la b%#$a (# ab%# la llaA# a($a d#a% "a#% "a(& $odo #l Aolm#! m#d&doa!$#( p? #? 18,0 "m3)? Go%a (# d#a "a#% #l NaOH o$a a o$a m!$%a( (# &mp%&m# al #%l#!m##% ! moA&-m!$o d# %o$a"&'!, a($a # #l &!d&"ado% A&%# d# "olo%? L# a!o$a #($# Aalo%? L# %#p&$# o$%a( do( A#"#( (# $oma"omo Aolm#! "o%%#"$o #l Aalo% m#d&o d# la( m#d&da( # m:( (# ap%o>&ma!?Ia$#%&al %#$a 1) d# 25 "m3%adada #! 0,1 "m3), p&p#$a 1) d# 20 "m3"o! a(p&%ado%, ma$%a #%l#!m##%1) d# 100 "m3, d&(ol"&'! d# al d# b%omo$&mol?@a b%#$a #( ! $bo #($%#"o %adado "o! !a bo"a (p#%&o% alo m:( a!"a pa%a ll#!a%lo !a llaA# d# pa(o#! la pa%$# &!D#%&o% pa%a pod#% Aa"&a%la?@a p&p#$a #( $amb&! ! $bo #($%#"o # p#d# (#% %adado o $#!#% !a ma%"a d# aDo%o? L# ll#!a al a(p&%a%"o! !a #(p#" d# #%&!a "a!do la bo"a &!D#%&o% m:( #($%#"a #($: (m#%&da #! la d&(ol"&'!?as"ados de una disolucin de 4Cl de concen"#acin $%1 ol/d&

5ue#on de @% @% @%@ c&% #esec"i2aen"e% F3u? concen"#acin "iene la disolucin de la -aseH-, Indi3ue el #ocediien"o se>uido desc#i-a el a"e#ial u"ili(ado en la dic6a 2alo#acin.

(P.A.U. Set. 10)

Rta.:a) [NaOH] = 0,098 mol/dm3

Solucin:

:l"lo d# la "o!"#!$%a"&'! d# la d&(ol"&'! d# NaOHL& lo( Aolm#!#( m#d&do( d# la d&(ol"&'! d# Hl D#%o! 9,8; 9,C 9,9 "m3, #l Aalo% "o%%#"$o (#%: la m#d&a

%= 9,8 "m3DHl

@a "o!"#!$%a"&'! d# la d&(ol"&'! d# NaOH (# "al"la d# la #($#&om#$%*a d# la %#a""&'!

Hl aq) + NaOH aq) K Nal aq) + H2O l)

@a "a!$&dad d# :"&do "lo%*d%&"o # %#a""&o!a #(

n (Hl)=9,8"m3DHl 0,10 mol Hl

1000"m3DHl

=9,8104 mol Hl

@a "a!$&dad d# &d%'>&do d# (od&o # %#a""&o!a #(

n (NaOH)=9,8104 mol Hl1mol NaOH

1 molHl =9,8104 mol NaOH

la "o!"#!$%a"&'! d# la d&(ol"&'! d# &d%'>&do d# (od&o #(

[NaOH]=9,8104 mol NaOH

10,0"m3

DNaOH

103"m

3

1,00dm3=0,098 mol NaOH /dm3D

%o"#d&m!$o d# Aalo%a"&'! o! !a p&p#$a (# m&d#! 10 "m3d# d&(ol"&'! d# NaOH (# A%$#! #! ! ma-$%a #%l#!m##% d# 100 "m3? L# aZad#! do( o$a( d# D#!olD$al#*!a la d&(ol"&'! (# AolA#%: d# "olo% %o(a D-"(&a? L# ll#!a !a b%#$a d# 25 "m3"o! d&(ol"&'! d# Hl 0,100 mol/dm3po% #!"&ma d#l "#%o? L# ab%# la llaA#

a($a # #l p&"o d# la b%#$a #($ ll#!o #l !&A#l #! "#%o? L# d#a! "a#% 9 "m3

(ob%# lo #%l#!m##% (# a&$a?L# ab%# la llaA# d# la b%#$a pa%a d#a% "a#% la d&(ol"&'! d# Hl #! p##Zo( "o%%o( m!$%a( (# &mp%&m# !moA&m!$o "&%"la% al #%l#!m##% a($a # #l "olo% d#l "o!$#!&do d#l #%l#!m##% d#(apa%#"a? L# a!o$a #l Ao-lm#! d# Hl a($ado p? #? 10,2 "m3) (# $&%a #l "o!$#!&do d#l #%l#!m##% (# laAa #l ma$%a? L# A#lA# a


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ll#!a% la b%#$a "o! Hl a($a #l "#%o? L# m&d#! o$%o( 10 "m3d# NaOH "o! la p&p#$a, (# A%$#! #! #l #%l#!m#-#% laAado p#%o !o !#"#(a%&am#!$# (#"o) (# aZad#! do( o$a( d# D#!olD$al#*!a? L# "olo"a #l #%l#!m##% baola b%#$a (# ab%# la llaA# a($a d#a% "a#% "a(& $odo #l Aolm#! m#d&do a!$#( p? #? 9,C "m 3)? Go%a (# d#a"a#% #l Hl o$a a o$a m!$%a( (# &mp%&m# al #%l#!m##% ! moA&m!$o d# %o$a"&'!, a($a # la D#!olD$al#*-!a p%da #l "olo%? L# a!o$a #($# Aalo%? L# %#p&$# o$%a( do( A#"#( (# $oma "omo Aolm#! "o%%#"$o #l Aalo% m#-d&o d# la( m#d&da( # m:( (# ap%o>&ma!?Ia$#%&al %#$a 1) d# 25 "m3%adada #! 0,1 "m3), p&p#$a 1) d# 10 "m3"o! a(p&%ado%, ma$%a #%l#!m##%

1) d# 100 "m3, d&(ol"&'! d# D#!olD$al#*!a?@a b%#$a #( ! $bo #($%#"o %adado "o! !a bo"a (p#%&o% alo m:( a!"a pa%a ll#!a%lo !a llaA# d# pa(o#! la pa%$# &!D#%&o% pa%a pod#% Aa"&a%la?@a p&p#$a #( $amb&! ! $bo #($%#"o # p#d# (#% %adado o $#!#% !a ma%"a d# aDo%o? L# ll#!a al a(p&%a%"o! !a #(p#" d# #%&!a "a!do la bo"a &!D#%&o% m:( #($%#"a #($: (m#%&da #! la d&(ol"&'!?


36/37


1). Indi3ue los #ocediien"os 3ue 6a u"ili(ado en el la-o#a"o#io a#a edi# el 4 de las disolucio0nes% seXalando las ca#ac"e#!s"icas de cada uno. Ci"e al>n eelo del eleo de indicado#eselicando el o# 3u? de su ca-io de colo#.

(P.A.U. Jun. 05)

Solucin:

o! &!d&"ado%#( :"&do-ba(# "omo la D#!olD$al#*!a o #l $o%!a(ol o #l a!a%a!ado d# m#$&lo, # adop$a! d&($&!-$o "olo% (#! #l pH? o% ##mplo la D#!olD$al#*!a #( &!"olo%a a pH M 8 p#%o $oma ! "olo% %o(a &!$#!(o (& #lpH ^ 10o! pap#l &!d&"ado% !&A#%(al, # Aa d# ! "olo% %oo &!$#!(o a pH =1 a($a "olo% al o("%o pa%a pH ^11?o! ! pHm#$%o, # "o!($a d# !a (o!da # (# &!$%od"# #! la d&(ol"&'! "o!#"$ada a ! &!d&"ado% "o!!a pa!$alla d&&$al #! la # apa%#"# #l Aalo% d#l pH?


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ndice de con"enidoCIDOS Y BASES.........................................................................................................................................1

efO@?@D0BASE DCB@.................................................................................................................................2

=8E?AS >?@D-BASE.........................................................................................................................2eR

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