Lesson 5 Hydrogen Halides.

A-level chemistry

1. The Hydrogen Halides.
Aim: To understand the bonding in hydrogen
halide molecules and the intermolecular forces
that exist between the molecules
To explain and identify the trend in boiling
points for Hydrogen halides.
To understand the acidic nature of the
hydrogen halides

2. The hydrogen halides………..
General formulas?
Describe how Hydrogen Chloride can be synthesised.
Record the equation for the reaction.
Test for Hydrogen halides?
Describe 3 general properties of the hydrogen halides.

3. Bonding in the hydrogen halides.
Dot and cross diagram for HF.
Distribution of Bonding Electron Pair.
The Covalent Bond in a Hydrogen halide molecule is Polar
Covalent.
This is due to the halogens having a higher electronegative
value than hydrogen.
Electronegativity is the ability of an element to attract a
pair of electrons in a covalent bond towards itself.

4. Trends in Electronegativity in the Periodic
Table.
Fluorine is most electronegative element.
Electronegativity decreases down a group.
Electronegativity increases across a period.

5. Types of Intermolecular Forces.
Dispersion forces – Non permanent dipole dipole
attractions.
Dipole – Dipole attractions.
Hydrogen Bonding.
Strongest?

6. Hydrogen Fluoride.
Types of intermolecular Forces?

7. Trends in Boiling Point.
Explain the anomalous behaviour of HF.
Explain the increase in Bpt from HBr – HI.

8. Chemical Reactions.
Reaction in Water.
Water soluble and acidic.
HCl.
HCl + H
2
O H
3
O
+
+ Cl
-1
HBr
HI
HI is the strongest acid – Why?