Acids and bases

1. ACIDS AND BASES

2. Properties: (other than tasting sour and being corrosive)
1) React with metals
2) React with carbonates
3) Conduct electricity
4) Turn blue litmus paper red
5) Neutralize bases
ACIDS ARE CORROSIVE
ACIDS

3. Acids react with various metals based on the activity series
1) ACIDS REACT WITH METALS
2HCl(aq) + Zn(s)  H2(g) + ZnCl2(aq)

4. What happens when you put baking soda (sodium bicarbonate) into
vinegar?
HC2H3O2(aq) + NaHCO3(aq)  CO2(g) + H2O(l) + NaC2H3O2(aq)
2) ACIDS REACT WITH CARBONATES

5. Acids are made of ions, so in water these ions separate and can conduct
electricity
HCl(aq)  H+
(aq) + Cl-
(aq)
3) ACIDS CONDUCT ELECTRICITY

6. H+
Cl-
H+
Cl-
H+
Cl-
Strong acids
ionize completely
in water, while
weak acids only
ionize slightly
3) ACIDS CONDUCT ELECTRICITY

7. NEGATIVELY-CHARGEDELECTRODE
POSITIVELY-CHARGEDELECTRODE
H+
Cl-
H+Cl-
H+
Cl-
H+
Cl-
- +
3) ACIDS CONDUCT ELECTRICITY

8. 4) ACIDS TURN BLUE LITMUS PAPER RED
Blue litmus paper is an indicator and turns red when it touches acid

9. Acids can neutralize bases, so adding an acid to a base can eliminate
their corrosiveness
HCl(aq) + NaOH(aq)  H2O(l) + NaCl(aq)
Hydrochloricacid+sodiumhydroxidewater+salt(sodiumchloride)
5) ACIDS NEUTRALIZE BASES

10. Properties: (other than tasting bitter, feeling slippery)
1) Conduct electricity
2) Turn red litmus paper blue
3) Neutralize acids
BASES ARE CAUSTIC
BASES

11. Bases are made of ions, so in water these ions separate and can conduct
electricity
NaOH(aq)  Na+
(aq) + OH-
(aq)
1) BASES CONDUCT ELECTRICITY

12. Red litmus paper is an indicator and turns blue when it touches base
2) BASES TURN RED LITMUS PAPER BLUE

13. Bases can neutralize acids, so adding a base to an acid can eliminate their corrosiveness.
(i.e. Antacids to neutralize stomach acid)
2HCl(aq) + CaCO3(aq)  CaCl2(aq) + H2CO3(aq)
H2CO3(aq) H2O(l) + CO2(g)
3) BASES NEUTRALIZE ACIDS

14. ACIDS:
1) Non-metal + oxygen  non-metal oxide
2) Non-metal oxide + water  ACID!
EXAMPLE:
N2 + 2O2  2NO2
NO2 + H2O  HNO3
BASES:
1) Metal + oxygen  Metal oxide
2) Metal oxide + water  BASE!
EXAMPLE:
Mg + O2  MgO
MgO + H2O  Mg(OH)2
HOW TO MAKE ACIDS AND BASES

15. Indicators change color depending on whether a substance is acidic or
basic
ACID-BASE INDICATORS

16. From 1 to 14, with 7 being neutral
pH SCALE

17. An acid is a substance that dissociates in water to
produce one or more hydrogen ions (H+
)
ex. HBr(aq)  H+
(aq) + Br-
(aq)
A base is a substance that dissociates in water to
form one or more hydroxide ions (OH-
)
ex. LiOH(aq)  Li+
(aq) + OH-
(aq)
ARRHENIUS THEORY OF ACIDS AND BASES

18. My theory has a
limitation…
HBr(aq)  H+
(aq) + Br-
(aq)
This reaction takes place in water! Without
water, acid properties and reactions can’t
exist.
A hydronium ion is actually produced (H3O+
)
to enable the effects of water.
HBr(aq) + H2O(l)  H3O+
(aq) + Br-
(aq) Arrhenius’s theory does
not account for the
hydronium ion
ARRHENIUS THEORY OF ACIDS AND BASES

19. …more like 2
limitations…
NH3(aq) is a base
and does not have OH
Actual reaction:
NH3(aq) + H2O(l)  NH4
+
(aq) + OH-
(aq)
Arrhenius’s theory does not account for bases
without OH groups
ARRHENIUS THEORY OF ACIDS AND BASES

20. An acid is a substance
from which a proton (H+
ion) can be removed
A base is a substance
that can remove a
proton (H+
ion) from an
acid
BRØNSTED-LOWRY THEORY OF ACIDS AND BASES

21. H2O(l) + HCl(aq)  H3O+
(aq) + Cl-
(aq)
Two molecules or ions that are related by the transfer of a proton
are called a conjugate acid-base pair
Conjugate acid-base pair
BRØNSTED-LOWRY THEORY OF ACIDS AND BASES

22. HBr(g) + H2O(l)  H3O+
(aq) + Br-
(aq)
Examples of conjugate acid-base pairs
Conjugate acid-base pair
Conjugate acid-base pair
BRØNSTED-LOWRY THEORY OF ACIDS AND BASES

23. NH3(g) + H2O(l)  NH4
+
(aq) + OH-
(aq)
Examples of conjugate acid-base pairs
Conjugate acid-base pair
Conjugate acid-base pair
BRØNSTED-LOWRY THEORY OF ACIDS AND BASES

24. Strong acid/base: dissociates completely in water
Examples: HCl, H2SO4 NaOH, Ba(OH)2
Weak acid/base: dissociates very slightly in water
Examples: CH3OOH (acetic acid) NH3
Conjugate acid-base pair
Conjugate acid-base pair Reversible…at equilibrium
STRONG AND WEAK ACIDS AND BASES

25. Monoprotic acid: Acid only has one hydrogen ion
Ex: HCl
Diprotic acid: Acid has two hydrogen ions
Ex: H2SO4
Triprotic acid: Acid has three hydrogen ions
Ex: H3PO4
MONOPROTIC, DIPROTIC, & TRIPROTIC ACIDS

26. Looking at a triprotic acid…
H3PO4
First ion dissociates: H3PO4(aq) + H2O(l) H3O+
(aq) + H2PO4
-
(aq)
Second ion dissociates: H2PO4
-
(aq) + H2O(l) H3O+
(aq) + HPO4
2-
(aq)
Third ion dissociates: HPO4
2-
(aq) + H2O(l) H3O+
(aq) + PO4
3-
(aq)
STRONGEST acid (easiest to dissociate)
WEAKEST acid (hardest to dissociate)
STRONG AND WEAK ACIDS AND BASES

27. If the pH is greater than 7, then the
substance is basic
If the pH is less than 7, then the
substance is acidic
NEUTRAL
POWER OF HYDROGEN (pH)

28. H2O(l) + H2O(l) H3O+
(aq) + OH-
(aq)
[H3O+
] = [OH-
] = 1.0 x 10-7
mol/L
In a neutral solution at 25ºC…
Concentration of H3O+
Concentration of OH-
pH
Negative
logarithm of…
Or
-log
Concentration
of H3O+
ions (in
mol/L)
Or
[H3O+
]
POWER OF HYDROGEN (pH)

29. Therefore pH of water = -log [H3O+
]
= -log [1.0x10-7
]
= -(-7.00)
= 7.00
POWER OF HYDROGEN (pH)

30. pH = - log [H3
O+
]
pOH = - log [OH-
]
[H3
O+] = 10 –pH
[OH-] = 10-pOH
pH + pOH = 14
Formulae involving pH:
POWER OF HYDROGEN (pH)

31. pOH = -log [OH-
]
= -log [3.8x10-3
]
= 2.42
pH = 14 – pOH
= 14 – (2.42)
= 11.58
Calculate the pH of a solution with [OH-
] = 3.8x10-3
mol/L
POWER OF HYDROGEN (pH)

32. Stoichiometry calculations:
1) Write the balanced chemical reaction
2) Convert all measurements to moles (if you can)
3) Work with molar ratios to find out how much an acid is needed to
neutralize a given amount of base, or vice versa.
HCl(aq) + NaOH(aq)  H2O(l) + NaCl(aq)
For example:
How many moles of HCl would you need to neutralize 2 moles of NaOH?
ANSWER: 2 moles of HCl
NEUTRALIZATION STOICHIOMETRY

33. What volume of 0.250 mol/L H2SO4(aq) is needed to react completely
with 37.2mL of 0.650mol/L KOH(aq)?
H2SO4(aq) + 2KOH(aq) 2H2O(l) + K2SO4(aq)
Step 1: Write the balanced chemical reaction
Step 2: Convert everything to moles
nKOH = C x V
= (0.650mol/L) x (0.0372L)
= 0.02418mol KOH
Step 3: Work with molar ratios
1mol H2SO4 = x
2mol KOH 0.02418mol KOH
x = 0.01209mol H2SO4
NOT DONE YET. Need to solve for volume of H2SO4
NEUTRALIZATION STOICHIOMETRY

34. V = n/C
= (0.01209mol)/(0.250mol/L)
= 0.04836L H2SO4
.: the volume of H2SO4 needed is 48.4mL
NEUTRALIZATION STOICHIOMETRY
What volume of 0.250 mol/L H2SO4(aq) is needed to react completely
with 37.2mL of 0.650mol/L KOH(aq)?

35. TITRATION

36. TITRATION
Purpose of titration: To
determine the unknown
concentration of the acid.

37. Equivalence point: The point (pH) in
the titration when an equal number of
moles of acid and base have been
added
End point: The point (pH) at which the
indicator changes colour indicating an
end to the titration
For a successful titration, choose an
indicator that changes colour at a pH
value close to the pH at the
equivalence point.
TITRATION

38. TITRATION CURVE

39. INDICATOR RANGES

40. Strong acid + Strong base titration: resulting solution has a pH = 7, so
bromothymol blue could be used (pH range is 6.0 – 7.6)
Weak acid + Strong base titration: resulting solution has a pH > 7 so
phenolphthalein could be used (pH range is 8.2 – 10.0)
Strong acid + weak base titration: resulting solution has a pH < 7 so
methyl orange could be used (pH range is 3.1 – 4.4)
INDICATOR RANGES

41. INDICATOR RANGES

42. LEWIS ACIDS AND BASES

43. Identify the acids and bases.
H2SO3(aq) + Ca(OH)2(aq)  CaSO3(s) + 2 H2O
Identify the acid and base.
CaO(s) + SO2(g)  CaSO3(s)
Are the two reactions the same?
acid base
Lewis acidLewis base
LEWIS ACIDS AND BASES

44. Not all acid-base reactions involve proton transfer.
acid – chemical substance that can accept a pair of
electrons to form a covalent bond
base – chemical substance that can donate a pair
of electrons to form a covalent bond
neutralization – formation of a covalent bond
between an acid and base reactant
LEWIS ACIDS AND BASES

45. a) H+
(aq) + OH-
(aq) <===> H2O(l)
b) NH3 + BCl3 
Lewis acid Lewis base
Lewis acidLewis base
BCl3:NH3
adduct: often formed between Lewis acids and bases, resulting in a single
product containing all atoms of all components.
LEWIS ACIDS AND BASES

46. c) sulfur dioxide + oxide ion  sulfite ion
d) Identify the Lewis acid and base given:
OH-
+ CO2  HCO3
-
SO2 + O2-
 SO3
2-
Lewis acid Lewis base
Lewis acidLewis base
LEWIS ACIDS AND BASES