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Unit 1 - Module 1
Lesson 8 – acids and bases
Objectives
Must
Identify acids, bases and alkalis and give the
formula of some common examples.
Could
Define the terms acid, base and alkali.
Should
Construct balanced symbol equations for the
dissolving of acid, bases and alkalis in water and
neutralisation reactions.
Spec statements
1.1.11a1 1 1h1
1a1 explain that an acid releases H+ ions in
aqueous solution;
1b1 state the formulae of the common acids:
hydrochloric, sulfuric and nitric acids;
1c1 state that common bases are metal oxides,
metal hydroxides and ammonia;
1d1 state that an alkali is a soluble base that
releases OH– ions in aqueous solution;
Starter
Using the universal indicator solution, work out
the pH of the common acids and alkalis in the
circus in the lab.
Construct a table before you begin. e.g.Name of substance Formula of
substance
Colour of indicator pH
Hydrochloric acid
Sodium hydroxide
Demo
Rainbow in a jar demonstration 1optional1
Theory - Acids
Definition of an acid 1 A proton donor.
When an acid is added to water, it releases H+
ions 1protons1 into the solution;
E.g. HNO1 1 H+ + NO1-
HHSOH 1 HH+ + SOHH-
The H+ ion is responsible for all acid reactions
that take place and is responsible for the pH of
the solution.
Activity
Learn the definition of an acid and the following
formulae;
1. Sulfuric acid - HHSOH
H. Nitric acid - HNO1
1. Hydrochloric acid - HCl
H. Phosphoric 1V1 acid - H1POH
5. Ethanoic acid - CH1COOH
Theory - Bases
Definition of a base 1 A proton acceptor
Common bases are metal oxides and metal
hydroxides. Ammonia and amines are also
bases.
Bases neutralise acids and have a pH higher
than 7.
Activity
Learn the definition of a base 1and an alkali1 and
the following formulae;
1. Sodium hydroxide - NaOH
H. Calcium hydroxide - Ca1OH1H
1. Magnesium oxide - MgO
H. Ammonia - NH1
5. Potassium hydroxide - KOH
AfL – using whiteboards
Quick test on formulae;
1. Ammonia
H. Potassium hydroxide
1. Sulfuric acid
H. Magnesium oxide
5. Calcium hydroxide
6. Nitric acid
are often called neutralisation reactions as the
pH of the products are neutral.
As well as water a salt is formed in the reaction
when the H+ ion of an acid is replaced by a
metal ion or NHH+.
E.g. Sodium hydroxide reacting with
hydrochloric acid;
NaOH + HCl 1 NaCl + HHO
Looking at the formation of the H products
individually;
Na+ + Cl- 1 NaCl
Here the H+ attached to the Cl- ion is replaced
by Na+ 1a metal ion1
OH- + H+ 1 HHO
This type of reaction can occur between acids
Practical
1. Carry out reactions of acids with metals,
carbonates, bases and alkalis.
H. Use small amounts in test tubes.
1. Record all observation carefully.
For each reaction write a balanced symbol
equation.
1. Recall the four general equations of the
formation of salts from metals, bases, alkalis
and carbonates.
H. Give an example of a balanced symbol
equation for each reaction above.
Write balanced symbol equations for the
following reactions;
1. Magnesium oxide + hydrochloric acid
H. Calcium carbonate + sulfuric acid
1. Potassium hydroxide + nitric acid
H. Ammonia + sulfuric acid
5. Sodium hydroxide + hydrochloric acid
Summary
Identify acids, bases and alkalis and give the
formula of some common examples.
Define the terms acid, base and alkali.
Construct balanced symbol equations for the
dissolving of acid, bases and alkalis in water and
neutralisation reactions.
Extension 1whole extra lesson1
• Determination of the relative atomic mass of a
metal by gas collection.
• For example weigh a sample of lithium and
react with water under a delivery
tube/inverted measuring cylinder and
measure the volume of hydrogen evolved.
• Then titrate solution to determine the
concentration of LiOH.
• Use this value and the volume of gas collected
to calculate Ar