Acids and Bases
Lactic acid

Citric acid

Common household
acids
Stearic acid
Ethanoic acid

Acetylsailicylic
Acid
Common laboratory acids






Hydrochloric acid
Nitric acid
Sulfuric acid
Phosphoric acid

-

HCl
HNO3
H2SO4
H3PO4
Arrhenius theory of acid






Arrhenius was a Sweedish
chemist
Put forward a theory of
acids in the 1880’s
Stated that...
Arrhenius theory of acid
For example: when HCl is added to
water:
HCl
H+ + ClIn general:
HA

H+

+

A-
Acids






HCl and HNO3 are monobasic acids as they donate
one H+ ion.
HNO3
H+
+ NO3-

H2SO4 is a dibasic acid as it d...


A strong acid is one which dissociates fully
in water
Example: HCl, H2SO4, HNO3
HCl + H2O
H3O+ + Cl-



A weak acid is...
Magnesium
hydroxide

Ammonia

Common household
bases
Sodium
hydroxide
Calcium hydroxide

Sodium hydrogen carbonate
Common laboratory bases






Sodium hydroxide
Calcium hydroxide
Ammonia
Sodium carbonate

-

NaOH
Ca(OH)2
NH3
Na2CO3
Arrhenius theory of bases






Arrhenius defined a base as:
A substance that dissociates in water to
produce OH- ions....


A strong base is one which dissociates
fully in water
Example: NaOH



A weak base is one which does not
fully dissoci...
Arrhenius theory


Combining:
HA
XOH

we get:
HA + XOH
acid + base

H+
X+

+
+

AOH-

AX + H2O
salt + water
Limitations of Arrhenius theory
1.

2.

3.

The acids and bases must be in aqueous
solutions (i.e. water). This prevents t...
Hydronium Ion









Arrhenius thought that an acid gives off H+ ions
in solution.
H+ ions are protons and can not ...
Brønsted-Lowry Theory


In 1923, Johannes Brønsted (a Danish
chemist) and Thomas Lowry (an English
chemist) proposed new ...
Brønsted-Lowry Theory


Brønsted and Lowry had worked
independently of each other but they both
arrived at the same defin...
Acid = Proton Donor
Donates a Proton

HCl

+

H2O

H3O+

+

Cl-

Accepts a Proton




The HCl donates a proton and so is...
Likewise:


HNO3

+ H2O

H3O+ +

NO3-

and



H2SO4 + H2O

H3O+ + HSO4-



HSO4- + H2O

H3O+ + SO4-2
Base = Proton Acceptor
Accepts a proton

NH3 + H2O

NH4+ + OHDonates a proton





The NH3 accepts a proton and so is a ...
Amphoteric




As can be seen from the previous two
examples, water is capable of acting
as both and acid and a base.
An...
Acid – Base Reaction

Acid – Donates Protons

HCl

+

NH3

Cl- + NH4+
Base – Accepts Protons
Neutralisation
The reaction between an acid and
a base to produce a salt and water
A salt is formed when the
hydrogen of a...
Neutralisation
Acid + Base

Salt + Water

HCl + NaOH
NaCl + H2O
but since the acid and base dissociate in water
we can wri...
Everyday Examples of Neutralisation

Indigestion remedies are
bases that neutralise excess
stomach acid

Lime is a base th...
Wasp stings are basic

Nettle, bee and ant stings
are acidic

They can be neutralised
with vinegar or lemon
juice

They ca...
Conjugate Acid-Base Pairs




Acids and bases exist in pairs called
conjugate acid-base pairs.
Every time an acid donate...
Likewise:
 When a base accepts a proton, it
becomes its conjugate acid.
Example:

NH3 + H2O

Base

NH4+ + OH-

Conjugate
...
Examples:
Conjugate
Acid

H2SO4 + H2O
Base

Base

HSO4- + H3O+

Conjugate
Acid

Conjugate

Acid

NH3

Base

+ H2 S

Base

...
Upcoming SlideShare
Loading in …5
×

4.2 acids and bases

2,409
-1

Published on

Published in: Education
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
2,409
On Slideshare
0
From Embeds
0
Number of Embeds
3
Actions
Shares
0
Downloads
65
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

4.2 acids and bases

  1. 1. Acids and Bases
  2. 2. Lactic acid Citric acid Common household acids Stearic acid Ethanoic acid Acetylsailicylic Acid
  3. 3. Common laboratory acids     Hydrochloric acid Nitric acid Sulfuric acid Phosphoric acid - HCl HNO3 H2SO4 H3PO4
  4. 4. Arrhenius theory of acid    Arrhenius was a Sweedish chemist Put forward a theory of acids in the 1880’s Stated that: An acid is a substance that dissociates in water to form H+ ions.
  5. 5. Arrhenius theory of acid For example: when HCl is added to water: HCl H+ + ClIn general: HA H+ + A-
  6. 6. Acids    HCl and HNO3 are monobasic acids as they donate one H+ ion. HNO3 H+ + NO3- H2SO4 is a dibasic acid as it donates two H+ ions. H2SO4 2H+ + SO42H3PO4 is a tribasic acid as it donates three H+ ions. H3PO4 3H+ + PO43-
  7. 7.  A strong acid is one which dissociates fully in water Example: HCl, H2SO4, HNO3 HCl + H2O H3O+ + Cl-  A weak acid is one which does not fully dissociate in water Example: CH3COOH (ethanoic acid) CH3COOH + H2O H3O+ + CH3COO-
  8. 8. Magnesium hydroxide Ammonia Common household bases Sodium hydroxide Calcium hydroxide Sodium hydrogen carbonate
  9. 9. Common laboratory bases     Sodium hydroxide Calcium hydroxide Ammonia Sodium carbonate - NaOH Ca(OH)2 NH3 Na2CO3
  10. 10. Arrhenius theory of bases    Arrhenius defined a base as: A substance that dissociates in water to produce OH- ions. For example: when NaOH is added to water: NaOH Na+ + OHIn general: XOH X+ + OH-
  11. 11.  A strong base is one which dissociates fully in water Example: NaOH  A weak base is one which does not fully dissociate in water Example: Mg(OH)2
  12. 12. Arrhenius theory  Combining: HA XOH we get: HA + XOH acid + base H+ X+ + + AOH- AX + H2O salt + water
  13. 13. Limitations of Arrhenius theory 1. 2. 3. The acids and bases must be in aqueous solutions (i.e. water). This prevents the use of other solvents benzene. Not all acid – base reactions are in solution, e.g. ammonia gas and hydrogen chloride gas produce ammonium chloride. According to Arrhenius, the salt produced should not be acidic or basic. This is not always the case, for example in the above reaction ammonium chloride is slightly acidic
  14. 14. Hydronium Ion      Arrhenius thought that an acid gives off H+ ions in solution. H+ ions are protons and can not exist independently. When the acid dissociates, the H+ ions react with water molecules: H + + H 2O H 3O+ The H3O+ ion is called the hydronium ion. This is another limitation of the Arrhenius theory.
  15. 15. Brønsted-Lowry Theory  In 1923, Johannes Brønsted (a Danish chemist) and Thomas Lowry (an English chemist) proposed new definitions of acids and bases. Brønsted Lowry
  16. 16. Brønsted-Lowry Theory  Brønsted and Lowry had worked independently of each other but they both arrived at the same definitions: An acid is a substance that donates protons (hydrogen ions). A base is a substance that accepts protons.
  17. 17. Acid = Proton Donor Donates a Proton HCl + H2O H3O+ + Cl- Accepts a Proton   The HCl donates a proton and so is an acid The H2O, in this case, accepts a proton and so is a base Remember: Proton = H+
  18. 18. Likewise:  HNO3 + H2O H3O+ + NO3- and  H2SO4 + H2O H3O+ + HSO4-  HSO4- + H2O H3O+ + SO4-2
  19. 19. Base = Proton Acceptor Accepts a proton NH3 + H2O NH4+ + OHDonates a proton   The NH3 accepts a proton and so is a base. The H2O, in this case, donates a proton and so is an acid.
  20. 20. Amphoteric   As can be seen from the previous two examples, water is capable of acting as both and acid and a base. Any substance that can act as both an acid and a base is said to be amphoteric.
  21. 21. Acid – Base Reaction Acid – Donates Protons HCl + NH3 Cl- + NH4+ Base – Accepts Protons
  22. 22. Neutralisation The reaction between an acid and a base to produce a salt and water A salt is formed when the hydrogen of an acid is replaced by a metal (or ammonium ion)
  23. 23. Neutralisation Acid + Base Salt + Water HCl + NaOH NaCl + H2O but since the acid and base dissociate in water we can write: H+ + Cl- + Na+ + OHNa+ + Cl- + H2O we can cancel the Na+ and Cl- on both sides leaving: H+ + OHH2O
  24. 24. Everyday Examples of Neutralisation Indigestion remedies are bases that neutralise excess stomach acid Lime is a base that neutralises acid in soil Toothpaste is a base that neutralises acid in the mouth
  25. 25. Wasp stings are basic Nettle, bee and ant stings are acidic They can be neutralised with vinegar or lemon juice They can be neutralised with baking soda
  26. 26. Conjugate Acid-Base Pairs   Acids and bases exist in pairs called conjugate acid-base pairs. Every time an acid donates/loses a proton, it becomes its conjugate base. Example: CH3COOH + H2O Acid CH3COO- + H3O+ Conjugate Base
  27. 27. Likewise:  When a base accepts a proton, it becomes its conjugate acid. Example: NH3 + H2O Base NH4+ + OH- Conjugate Acid
  28. 28. Examples: Conjugate Acid H2SO4 + H2O Base Base HSO4- + H3O+ Conjugate Acid Conjugate Acid NH3 Base + H2 S Base NH4+ + HS- Conjugate Acid
  1. A particular slide catching your eye?

    Clipping is a handy way to collect important slides you want to go back to later.

×