The pink colour in test tubes #2 and #4 was caused by the basic solution (NaOH) reacting with the phenolphthalein indicator, which turns pink in basic solutions with a pH between 8.2-12. The colour disappeared in test tube #5 because the acidic solution (HCl) was added, and phenolphthalein is colourless in acidic solutions below pH 8.2. We could use an acidic solution like HCl to take away the pink colour in test tube #6, as it would neutralize the basic solution and lower the pH below 8.2, making the phenolphthalein colourless again.

1. Chemistry
Chapter 3 - Section 3
Acidic and
Basic Solutions


2. What are some
common acids?
vinegar oranges
lemons
hydrochloric sulfuric
acid acid

3. Properties of Acids
๏Tastes Sour
๏Conducts Electricity
๏The hydronium ions in an acidic solution can
carry the electric charges in a current
๏Corrosive
๏They can break down certain substances. Many
acids can corrode fabric, skin, and paper.

4. Properties of Acids
๏React with metals
๏ The solutions of some acids also react
strongly with certain metals.
๏ The acid-metal reaction forms metallic
compounds and hydrogen gas, leaving
holes in the metal in the process.

5. Uses of Acids

6. Uses of Acids
Acetic Acid

7. Uses of Acids
Citric Acid

8. Uses of Acids
Ascorbic
Acid

9. Uses of Acids
Sulfuric Acid

10. Uses of Acids
Acids often are used in batteries because their
solutions conduct electricity

11. Uses of Acids
Hydrochloric acid, which is known
commercially as muriatic acid, is used
in a process called pickling. Pickling is
a process that removes impurities
from the surfaces of metals.

12. Acidsin the
Environment
Carbonic
acid
plays a key role in
the formation of
caves and of
stalactites and
stalagmites.

13. Acidsin the
Environment
Carbonic acid is
formed when
carbon dioxide in
soil is dissolved in
water.

14. Acidsin the
Environment
When this acidic
solution comes
in contact with
calcium
carbonate—or
limestone rock
—it can dissolve
it, eventually
carving out a
cave in the rock.

15. Acids ?

16. Substances that RELEASE positively
charged hydrogen ions, H+, in water.

17. When an acid mixes with
water, the acid dissolves,
releasing a hydrogen ion.

18. The hydrogen ion then
combines with a water
molecule to form a
hydronium ion, H30+.

19. Hydronium Ion ?

20. positively charged ion with
the formula H3O+

23. Bas
es

24. Properties of Bases
๏Basic solutions feel slippery.
๏Bases also taste bitter.
๏Like acids, bases are corrosive.
Basic solutions contain ions and can
conduct electricity.
๏Basic solutions are not as reactive with
metals as acidic solutions are.

25. Where do we find
Bases?
soaps, ammonia, cleaning products

26. Where do we find
Bases?
The hydroxide ions produced by bases can interact
strongly with certain substances, such as dirt and grease.

27. Where do we find
Bases?
chalk

28. Where do we find
Bases?
blood

29. Bases?

30. substances that can
ACCEPT hydrogen ions.

31. Do you remember the
definition of an acid?

32. Substances that
RELEASE positively
charged hydrogen
ions, H+, in water.

33. Substances that release positively
charged hydrogen ions, H+, in water.
Acids
Bases
Substances that can accept hydrogen
ions.

34. When a base dissolves in water,
some hydrogen atoms from the
water molecules are attracted to
the base.

35. A hydrogen atom in the water
molecule leaves behind the
other hydrogen atom and
oxygen atom.

37. What is left of the H2O is the OH-, which
an ion called a hydroxide ion.
OH -

38. Most bases contain a
hydroxide ion, which is
released when the base
dissolves in water.

39. For example, sodium hydroxide is a base with the
formula NaOH. When NaOH dissolves in water,
a sodium ion and the hydroxide ion separate.

41. pH

42. pH??

43. a measure of how
acidic or basic a
solution is

44. pH
๏The pH scale ranges from 0 to 14.
๏Acidic solutions have pH values below 7.
๏A solution with a pH of 0 is very acidic.
๏A solution with a pH of 7 is neutral.
๏Basic solutions have pH values above 7.

45. pH

46. A change of 1 pH unit represents a tenfold
change in the acidity of the solution.

47. For example, if one solution has a pH of 1
and a second solution has a pH of 2, the
first solution is not twice as acidic as the
second—it is ten times more acidic.

48. To determine the difference in pH strength,
use the following calculation:
10n,
where
n = the difference between pHs.
For example: pH3 - pH1 = 2
102 = 100 times more acidic.

49. Strength of
Acids and Bases
๏The difference between food acids and the
acids that can burn you is that they have
different strengths.

50. Strength of Acids and Bases

51. Hydrochloric acid separates into ions
more readily than acetic acid does
when it dissolves in water.
The more easily a H+ ion is released,
the stronger the acid is.

52. Therefore, hydrochloric acid exists in water
as separated ions. Acetic acid exists in
water almost entirely as molecules.

53. More hydronium ions means a stronger-
acid solution. It would have a lower pH
than the weak-acid solution.

54. The strength of a base is related to
how easily the base accepts H+, or
how easily a hydroxide ion is made,
when the base dissolves in water.

56. Indica
tors

57. Indicators??

58. are compounds that react
with acidic and basic solutions
and produce certain colours,
depending on the solution’s
pH.

59. Because they are different
colors at different pHs,
indicators can help you
determine the pH of a
solution.

60. When litmus paper is placed
in an acidic solution, it turns
red. When placed in a basic
solution, litmus paper turns
blue.

63. Neutra
lizatio
n

64. Neutralization??

65. the reaction of an acid with a base. It is called this
because the properties of both the acid and base
are diminished, or neutralized.

66. In most cases, the
neutralization reaction
produces a water and a
salt.

67. How does
neutralization occur??
๏Recall that every water molecule
contains two hydrogen atoms and one
oxygen atom.
๏When one hydronium ion reacts with
one hydroxide ion, the product is two
water molecules. This reaction occurs
during acid-base neutralization.

68. How does
neutralization occur??

69. How does
neutralization occur??
๏Equal numbers of hydronium ions from
the acidic solution and hydroxide ions
from the basic solution react to produce
water.
๏Pure water has a pH of 7, which means
that it’s neutral.

71. Funny Colours
1 2 3 4 5 6
phenolphthalein

72. Funny Colours
1 2 3 4 5 6
Phenolphthalein is an indicator
pH 0−8.2 8.2−12.0 >12.0
Conditions acidic or near-neutral basic strongly basic
Color colorless pink to fuchsia colorless
phenolphthalein

73. Funny Colours
1 2 3 4 5 6
NaOH NaOH

74. Funny Colours
1 2 3 4 5 6
NaOH
A basic solution which will be
colourless in the presence of phenolphthalein.
pH 0−8.2 8.2−12.0 >12.0
Conditions acidic or near-neutral basic strongly basic
Color colorless pink to fuchsia colorless
NaOH NaOH

75. Funny Colours
1 2 3 4 5 6
HCl

76. Funny Colours
1 2 3 4 5 6
HCl
An acidic solution which will be
colourless in the presence of phenolphthalein.
pH 0−8.2 8.2−12.0 >12.0
Conditions acidic or near-neutral basic strongly basic
Color colorless pink to fuchsia colorless
HCl

77. Funny Colours
What made the pink colour in #2 and 4?
What made the colour disappear in test tube #5?
What could we use to take away the pink colour
in test tube #6?