Acids, bases, and salts are fundamental concepts in Chemistry 12, focusing on their properties, reactions, and applications. This unit explores the Arrhenius and Bronsted-Lowry theories, detailing how acids and bases interact in various chemical reactions. Students will learn about common acids and bases, their uses, and the significance of pH in chemical processes. The notes also cover titration methods, buffer solutions, and the impact of acid rain on the environment. Ideal for high school chemistry students preparing for exams.

Key Points

  • Explains the Arrhenius and Bronsted-Lowry theories of acids and bases.
  • Covers common acids and bases, including their properties and uses.
  • Discusses the importance of pH and titration methods in chemistry.
  • Examines buffer solutions and their role in maintaining pH levels.
  • Highlights the environmental effects of acid rain and its sources.
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Chemistry 12
Unit IV – Acids, Bases and Salts
Notes
IV.1 – The Arrhenius Theory Of Acids and Bases
• Acid: any substance which releases H
+
(aq)
in water.
• Base: any substance which releases OH
-
(aq)
in water.
• Salt: is the neutralization product which results when an acid and a base react:
HCl
(aq)
+ NaOH
(aq)
NaCl
(aq)
+ H
2
O
(l)
acid + base salt + water
In more general terms, a salt is any ionic compound which is neither an acid nor a base.
• The following is a more simple way to think of Arrhenius acids, bases and salts. (There are some
exceptions)
An ACID is any ionic species whose formula starts with an “H”.
Examples: HCl, HNO
3
, H
2
SO
4
A BASE is any ionic species whose formula ends with an “OH”
Examples: NaOH, KOH, Ca(OH)
2
, Zn(OH)
2
A SALT is any ionic species which does not start with an “H” or end with an “OH”.
Examples: KBr, FePO
4
, Li
2
CO
3
How to write and balance acid-base neutralization reactions.
• Since we know that: ACID + BASE SALT + WATER, we can use the following procedure.
All neutralization reactions are based on the fact that acids produce H
+
and bases produce OH
-
.
Therefore, the main reaction which occurs in every instance is just:
H
+
+ OH
-
H
2
O
Example: Write the neutralization reaction that occurs between HCl and Ca(OH)
2
.
• General Properties of Acids and Bases
The presence of H
+
accounts for these properties of acids:
a) acids react with bases.
b) acids are electrolytes.
c) acids react with some metals to produce H
2(g)
.
d) acids turn litmus paper RED.
e) acids taste SOUR. (e.g. lemon juice, vinegar)
Simmer Down Inc.© (Portions taken from KineticsNotes-JKK-99, Hebden: Chemistry 12…) 1
The presence of OH
-
accounts for these properties of bases:
a) bases react with acids.
b) bases are electrolytes.
c) bases feel slippery. (React with your fat to make soap.)
d) bases turn litmus paper BLUE.
e) bases taste BITTER. (e.g. baking soda)
A mnemonic for remembering the litmus colours:
Litmus paper is: RED
in ACID
B
LUE in BASE
Examples:
1. August 2003
2. June 2004
3. August 1998
4. August 2001
***Do Hebden Questions #1 - 4, pgs 110 - 112***
Simmer Down Inc.© (Portions taken from KineticsNotes-JKK-99, Hebden: Chemistry 12…) 2
Simmer Down Inc.© (Portions taken from KineticsNotes-JKK-99, Hebden: Chemistry 12…) 3
IV.2 - Some Common Acids and Bases
• Sulphuric Acid (H
2
SO
4
) Commercial names: oil of vitriol, “battery acid”
Properties:
good dehydrating agent (removes water from substances)
strongly exothermic reaction when mixed with water
chars some types of organic material (e.g., sugars) when in
concentrated form, as a result of dehydrating action (turns skin black on contact)
reacts with some metals, but often slowly
good electrolyte (conducts electricity)
concentrated Sulphuric acid is 98% H
2
SO
4
and 2% water (18 M H
2
SO
4
)
Common uses:
production of sulphates
manufacturing fertilizers, explosives, plastics, insecticides,
used in car batteries as an electrolyte
• Hydrochloric Acid (HCl) Commercial name: muriatic acid
Properties:
concentrated HCl turns skin white on contact
good electrolyte
concentrated solutions have a choking odour
reacts with some metals, but often slowly
concentrated hydrochloric acid is 37% HCl in water (12 M)
Common uses:
production of chlorides
cleaning metal products (removes metal oxides)
“stomach acid” is a dilute solution of HCl; stomach acid
activates a protein-digesting biological catalyst “enzyme”
removing scale from boilers (“boiler scale” consists of calcium and magnesium carbonate)
• Nitric Acid (HNO
3
) Commercial name: (none, other than “nitric acid”)
Properties:
colours protein yellow (this is a non-specific test for the presence of protein). Hence, turns skin
yellow on contact.
very reactive, quickly attacks almost all metals
concentrated nitric acid is 69% HNO
3
in water (16 M)
Common uses:
production of nitrates
manufacturing fertilizers, explosives, dyes
• Acetic Acid (CH
3
COOH) Commercial name: 5% aqueous solution is called “vinegar”
Properties:
non-electrolyte when concentrated (99 - 100%, 17 M); weak electrolyte when diluted
corrosive, burns skin
only affects highly reactive metals
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FAQs

What are the main properties of acids and bases?
Acids are substances that release hydrogen ions (H+) in solution, while bases release hydroxide ions (OH-). Common properties of acids include a sour taste, the ability to turn litmus paper red, and their reactivity with metals to produce hydrogen gas. Bases, on the other hand, tend to taste bitter, feel slippery, and turn litmus paper blue. Understanding these properties is essential for identifying and working with various acids and bases in chemical reactions.
How do titrations work in acid-base chemistry?
Titrations are analytical techniques used to determine the concentration of an unknown acid or base by reacting it with a standard solution of known concentration. During a titration, an indicator is often used to signal the endpoint, where the amount of acid equals the amount of base. The equivalence point is crucial as it indicates that the reaction is complete. By measuring the volume of titrant used, students can calculate the concentration of the unknown solution.
What role do buffers play in chemical solutions?
Buffers are solutions that resist changes in pH when small amounts of acids or bases are added. They typically consist of a weak acid and its conjugate base or a weak base and its conjugate acid. For example, a mixture of acetic acid and sodium acetate forms a buffer that maintains a stable pH. Buffers are vital in biological systems, as they help maintain the pH of blood and other bodily fluids, ensuring proper physiological function.
What is the significance of pH in acid-base chemistry?
pH is a measure of the hydrogen ion concentration in a solution and indicates whether a solution is acidic, neutral, or basic. A pH less than 7 indicates acidity, while a pH greater than 7 indicates basicity. Understanding pH is crucial in various chemical processes, including titrations and buffer solutions. It also plays a significant role in environmental chemistry, as changes in pH can affect aquatic life and soil health.
What are the environmental impacts of acid rain?
Acid rain occurs when pollutants such as sulfur dioxide and nitrogen oxides react with water vapor in the atmosphere, resulting in precipitation with a pH lower than 5.6. This acidic rain can harm aquatic ecosystems, damage forests, and erode buildings and monuments. Additionally, acid rain leaches essential minerals from soil and water, disrupting nutrient cycles. Addressing the sources of acid rain is critical for environmental conservation and public health.

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