IGCSE Chemistry Section 4 Lesson 1
IGCSE Chemistry Section 4 Lesson 1
IGCSE Chemistry Section 4 Lesson 1
SECTION 4 LESSON 1
Content
The iGCSE
Section 1 Principles of Chemistry
Chemistry
course Section 2 Chemistry of the Elements
Section 4
a) Acids, alkalis and salts
b) Energetics
Physical c) Rates of reaction
Chemistry d) Equilibria
4.1 describe the use of the indicators litmus, phenolphthalein and
Lesson 1
methyl orange to distinguish between acidic and alkaline solutions
4.2 understand how the pH scale, from 0–14, can be used to classify
solutions as strongly acidic, weakly acidic, neutral, weakly alkaline
or strongly alkaline
a) Acids,
4.3 describe the use of universal indicator to measure the
approximate pH value of a solution
alkalis 4.4 define acids as sources of hydrogen ions, H+, and alkalis as
sources of hydroxide ions, OH¯
and salts 4.5 predict the products of reactions between dilute hydrochloric,
nitric and sulfuric acids; and metals, metal oxides and metal
carbonates (excluding the reactions between nitric acid and metals)
4.6 understand the general rules for predicting the solubility of salts
in water:
i all common sodium, potassium and ammonium salts are soluble
ii all nitrates are soluble
iii common chlorides are soluble, except silver chloride
iv common sulfates are soluble, except those of barium and calcium
v common carbonates are insoluble, except those of sodium,
potassium and ammonium
4.7 describe experiments to prepare soluble salts from acids
4.8 describe experiments to prepare insoluble salts using
precipitation reactions
4.9 describe experiments to carry out acid-alkali titrations.
pH scale and indicators
The pH scale is a measure of how acidic or alkaline a solution is.
pH scale and indicators
The pH scale is a measure of how acidic or alkaline a solution is.
ACIDIC ALKALINE
neutral
Very Slightly Slightly Very
1 2 3 4 5 6 7 8 9 10 11 12 13 14
pH scale and indicators
The pH scale is a measure of how acidic or alkaline a solution is.
ACIDIC ALKALINE
neutral
Very Slightly Slightly Very
1 2 3 4 5 6 7 8 9 10 11 12 13 14
A substance forms an aqueous solution when it dissolves
in water. Water itself is neutral.
H+(aq) OH-(aq)
acid alkali
pH scale and indicators
Indicators are special dyes that change colour
according to whether they are in acidic, alkaline
or neutral solutions.
pH scale and indicators
Indicators are special dyes that change colour
according to whether they are in acidic, alkaline
or neutral solutions.
Litmus
Phenolphthalein
Methyl Orange
pH scale and indicators
Litmus
ACIDIC ALKALINE
neutral
Very Slightly Slightly Very
1 2 3 4 5 6 7 8 9 10 11 12 13 14
5.0 8.0
pH scale and indicators
Methyl Orange
ACIDIC ALKALINE
neutral
Very Slightly Slightly Very
1 2 3 4 5 6 7 8 9 10 11 12 13 14
4.4 6.2
pH scale and indicators
Phenolphthalein
ACIDIC ALKALINE
neutral
Very Slightly Slightly Very
1 2 3 4 5 6 7 8 9 10 11 12 13 14
8.3 10
pH scale and indicators
Universal indicator is a mixture of dyes, and
shows a complete colour range across the pH
scale.
Common acids and alkalis
ACIDS
Name Formula
Hydrochloric acid HCl
Sulphuric acid H2SO4
Nitric acid HNO3
Common acids and alkalis
ACIDS
Name Formula
Hydrochloric acid HCl
Sulphuric acid H2SO4
Nitric acid HNO3
ALKALIS
Name Formula
Sodium hydroxide NaOH
Potassium hydroxide KOH
Calcium hydroxide Ca(OH)2
Salt formation
When acids and alkalis react together,
salts are formed.
Non-metal
Salt Formula Metal ion
ion
Copper CuSO4 SO42-
Cu2+
sulphate
Sodium
NaCl Na+ Cl-
chloride
Potassium KNO3 NO3-
K+
nitrate
Calcium CaSO4 SO42-
Ca2+
sulphate
Reactions of salts
Acids + Metals
Mg + 2HCl MgCl2 + H2
Reactions of salts
Acids + Metals
Guess what?
That’s right, no
more examples!
Solubility of salts
If a substance is soluble, then this means that it
will dissolve in a solvent.
Solubility of salts
If a substance is soluble, then this means that it
will dissolve in a solvent.
Solution (aqueous)
Solubility of salts
Carrying out
acid-alkali
titrations
Preparing soluble salts from acids
Eg. the preparation of sodium chloride by neutralization
Preparing soluble salts from acids
Eg. the preparation of sodium chloride by neutralization
Dilute Dilute
sodium hydrochloric
hydroxide acid
+ indicator
solution
Preparing soluble salts from acids
Eg. the preparation of sodium chloride by neutralization
Filtrate
Decolourising
charcoal Evaporating
basin
Preparing soluble salts from acids
Eg. the preparation of sodium chloride by neutralization
Crystals of
sodium
chloride Acid + Alkali
forming) Salt + Water
Filtrate
Steam
HCl(aq) + NaOH(aq)
Water bath
NaCl(aq) + Water(l)
Bunsen
burner
Preparing insoluble salts using
precipitation reactions
Eg. the preparation of lead iodide
Preparing insoluble salts using
precipitation reactions
Eg. the preparation of lead iodide
Lead
iodide
Preparing insoluble salts using
precipitation reactions
Eg. the preparation of lead iodide
A titration is a
very accurate way
of adding an acid
to an alkali to get
a salt.
Acid – Alkali Titrations
To carry out an acid-alkali titration we need
the right bits of kit.
Conical
flask
Acid – Alkali Titrations
To carry out an acid-alkali titration we need
the right bits of kit.
Pipette
Acid – Alkali Titrations
To carry out an acid-alkali titration we need
the right bits of kit.
Burette
Acid – Alkali Titrations
Stage 1
meniscus
Dilute sodium hydroxide (NaOH)
solution is sucked up into a pipette
using a pipette filler. The pipette
contains exactly 25.0cm3 of
solution when the bottom of the
meniscus is level with the pipette
mark. The sodium hydroxide
solution is then released in to the
conical flask.
Acid – Alkali Titrations
Stage 1
meniscus
Dilute sodium hydroxide (NaOH)
solution is sucked up into a pipette
using a pipette filler. The pipette
contains exactly 25.0cm3 of
solution when the bottom of the
meniscus is level with the pipette
mark. The sodium hydroxide
solution is then released in to the
conical flask.
Acid – Alkali Titrations
Stage 2
Carrying out
acid-alkali
titrations
Preparing
insoluble salts
using
Preparing
precipitation
soluble salts
reactions
from acids
Carrying out
acid-alkali
titrations
Preparing
insoluble salts
using
Preparing
precipitation
soluble salts
reactions
from acids
Carrying out
acid-alkali
titrations
End of Section 4 Lesson 1
Preparing salts