Summary Final base

1¥
CHEM
Acids and Bases




Zainab Madan

, Acids and Bases:
Zainab Modan


Properties of Acids and Bases: Acids Bases


-sour taste -bitter taste
-watery -slippery feel
-react with -turns red litmus
-turn blue litmus paper red
litmus paper blue
-react with carbonates to
-are compounds -don’t react with
form CO. bubbles
-release ions in carbonates
-react with metals —> form
solution -react with acids
hydrogen gas
-form salt and -separates into
-react with bases
water when hydroxide ions (OH-)
-separates into hydrogen ions
combined in water
(H+) in water
-pH<7 -pH>7




Bronsted-Lowry Acids and Bases: →
acids and bases can be seen as proton transfer reactions:
>Acid- proton donor ↳ Acid →
proton donating species
>Base- proton acceptor ↳ Base →
proton accepting species


NHI Cl
-




① Hclcg) + NHS (g) t NHc.cl ( s )




Hydrogen atom:
e-
,




+
H+ is merely a bare proton, therefore it interacts strongly with any source
proton of electron density such as non-binding electron pairs




Conjugate Acid-Base Pairs: "
after a reaction ,
the acid becomes a base be the base becomes the acid
"




-A conjugate acid-base pair consists of two species in an acid-base reaction (one acid and one base) that
differ by the loss or gain of a proton.

↳ NH } ( ag ) + Hzocaq , Nhut caq ) + OH
-




Caq )
Base Acid Acid Base
r r 7 7




*
What has more
Hydrogen atoms than NHS . : Acid =
Nhut
H2O Acid
has
Hydrogen OH
-

*
more atoms than .
: =
Hzo


Conjugate Acid-Base pairs:
} NHI H2O 4 OH
-

°
NHS o




"
↳ COs HCO
-




OH
-




caq ) + Hzo (e) } Cag, +
caq )

Base Acid Acid Base Conjugate Acid-Base pairs:
r
7 7
r o


he
>
cos
-




1-105
o
Hzo 7 OH
-

,-A strong acid is linked to a weak conjugate base and vice versa conjugate
acid

- HCl : conjugate base is Cl-
>HCl is a strong acid & therefore has a great tendency to HSPQ ,
-
add an H b add at
charge
→
ionise and donate protons HZPOI
>It’s conjugate base is weak because it wants to remain ↳ -
HPa 7 accept
ions and have a low tendency to gain protons .
-
take away an H
① charge
conjugate base . : -2
charge




(a) What is the
conjugate base of Hcloc , ,
Hzs ,
Phat ,
HCo5 ?
↳ Hcloc ,
↳ Has ↳ PHI ↳ Has
-




PH } :[ 032
' -




HS
-




CJ base : [ 104 CJ base : CJ base : CJ base



(b) acid of SOI
-




Hcoj ?
what the
conjugate Hzo
-



is CN , ,
,



↳ CN ↳ 5042 ↳ Hzo
- - -




↳ NCOs
'_
-




CJ acid : HCN CJ acid : 1-1504 CJ acid : 1-130 CJ acid :
Hzcos


Ampholytes:
Amphiprotic species: a species that can act as either an acid or a base (it can lose or gain a proton), depending on the other reactant

↳ consider water :




Hzo
-




OH acting acid
-




+ CHSO t CHSOH : water as an

lone pair of é
a
acid acid
bag
base
g.
'
( can accept a
proton )


H H
←
Hydrogen atom
Hzo HBR H3O+ Bri i.
water base
acting
+
Kan donate a + as a

proton ) d
ba base




↳
Hydronium ion :




0in solutions H+ interacts with Hzo to form 1-130
+ ( hydronium ion )
aqueous



+



H+ + H , H H

H
H




Exercise 16.2 Writing Equations for Proton-Transfer Reactions
• The hydrogen sulfite ion (HSO3-) is amphiprotic. Write an equation for the reaction of HSO3- with water
(a) in which the ion acts as an acid and (b) in which the ion acts as a base. In both cases identify the conjugate acid–base pairs.
(a)
Hsot
"

1-1505 + 1-120 503 t


(b) 1-1505 Hzsoz
-




+ Hzo 1- OH


• When lithium oxide (Li O) is dissolved in water, the solution turns basic
2




from the reaction of the oxide ion (O ) with water. Write the equation for this reaction and identify the conjugate acid–base pairs.
2-




When lithium oxide (Li2O) is dissolved in water, the solution turns basic from the reaction of the oxide ion (O2 )
with water. Write the equation for this reaction and identify the conjugate acid–base pairs.
Answer: O2-(aq) + H2O(l) —>OH-(aq) + OH-(aq). The OH- is both the conjugate acid of O2- and the conjugate
base of H2O.

, Relative strengths of acids and bases:


-Strong acids and bases dissociated
completely in water
-Weak acids and bases dissociate only
partially in water
-Substances with negligible acidity do not
dissociate in water (release H+)
-The strongest acids have the weakest
conjugate bases (Kw)
And the strongest bases have the weakest
conjugate acids


-Substances with negligible acidity (contains hydrogen but doesn’t demonstrate acidic
behavior in water) do not dissociate in water—>the conjugate base of a substance with negligible acidity is a strong base
- The leveling effect—> stronger acids react with water to form H+ ions and stronger bases react with water to form OH− ions
-In every acid base reaction, equilibrium favors transfer of the proton from the stronger acid to the stronger base to from the weaker
acid and the weaker base
Autoprotolysis / Autoionisation of H2O :
Water undergoes self- ionisation since H2O acts as an acid and a base

Hsoctae, OH
-




Hzoiet Hz Ole, +
cag,



The equilibrium Constants expression for this reaction is :

Kc=[Hs0+][ OH ]
-




=
kkwwc ion -


product constant of water
=
1.0×10-14 @ 25°C the extent of
autoprolysis is
very small .




Using Kw you can calculate concentrations of H3O+ and OH- in pure water:

[1-130+3101-1] 1.0
" " If you add an acid or a base to water the concentrations of
=
✗ 10

[ 1-130+1=[01-5]--1.0
H3O+ and OH- will no longer be equal. But Kw will still hold
in pure water ✗ 10-7 M


0


Exercise 16.4 Calculating [H+] for Pure Water• Calculate the values of [H+] and [OH-] in a neutral solution at 25 C

kW = 1.0 × 10-14


( Ht ) [01-1]=1.0×10-14
[ Ht ] 1.0×10-7
,M
. : =