1. Recap – Formula and bonding
Chem 1001 Lecture 4
Recap – Formula and bonding
Types of bonding: ionic, covalent, metallic
Types of formula: empirical, molecular, structural
Type of covalent materials: molecular, network HO
H2O2

2. Polarity of Water The O-H bonds in water are polar.
Chem 1001 Lecture 9
Polarity of Water
The O-H bonds in water are polar.
The angular shape of the molecule mean water is a ‘polar molecule’.
Fig. 4.2 Silberberg
Dr Toby Hudson

3. Chemical Reactions Chemical reactions occur because:
Chem 1001 Lecture 10
Chemical Reactions
Chemical reactions occur because:
Products contain less energy than reactants and systems go to lowest energy state, eg burning gas.
Energy supplied to force reactants to products which have higher energy, eg blast furnace.
Dr Toby Hudson

4. Chemical Equations Word Equation hydrogen plus oxygen forms water
Chem 1001 Lecture 10
Chemical Equations
Word Equation
hydrogen plus oxygen forms water
Symbolic Equations – use correct formula
H2 + O2  H2O
Need to balance equations. Indicate states
2H2(g) + O2(g)  2H2O(l)
Dr Toby Hudson

5. Chemical Equations Molecular Equation eg H2(g) + I2(g)  2HI(g)
Chem 1001 Lecture 10
Chemical Equations
Molecular Equation
eg H2(g) + I2(g)  2HI(g)
C6H12O6(s)  C6H12O6(aq)
Ionic Equations
eg NaCl (s)  Na+(aq) + Cl-(aq)
Pb2+(aq) I-(aq)  PbI2(s)
Precipitate
Dr Toby Hudson

6. Reactions with Acid, H+ H+ H+ cation is just a ‘bare proton’, no e-.
Chem 1001 Lecture 11
Reactions with Acid, H+
- e- H+
Hydrogen
atom
ion
H+ cation is just a ‘bare proton’, no e-.
In aqueous solution, H+ associates with H2O to give H3O+(aq), also called H+(aq). + O H
Substances that provide H+ ions in water are called ACIDS.
Dr Chiara Neto

7. Metal + Acid  Salt + Hydrogen
Chem 1001 Lecture 11
Metal + Acid  Salt + Hydrogen
Formula Equation
Zn + 2HCl  ZnCl H2
Complete ionic equation  
Zn(s) + 2H+(aq) + 2Cl-(aq)  Zn2+(aq) + H2(g) + 2Cl-(aq)
Net ionic equation
Zn(s) + 2H+(aq)  Zn2+(aq) + H2(g)
We can isolate the salt by evaporation of the solvent
Zn2+(aq) + 2Cl-(aq)  ZnCl2(s)
Dr Chiara Neto

8. Carbonate + Acid  Salt + H2O + CO2
Chem 1001 Lecture 11
Carbonate + Acid  Salt + H2O + CO2
Formula Equation
CaCO HCl  CaCl H2O CO2
Complete ionic equation  
CaCO3(s) +2H+(aq) + 2Cl-(aq)  Ca2+(aq) + H2O(l) CO2(g) + 2Cl-(aq)
Net ionic equation
CaCO3(s) + 2H+(aq)  Ca2+(aq) + H2O(l) + CO2(g)
We can isolate the salt by evaporation of the solvent
Ca2+(aq) + 2Cl-(aq)  CaCl2(s)
Dr Chiara Neto

9. Learning Outcomes: By the end of this lecture, you should:
understand the reason that water dissolves some ionic materials
know the component parts of a chemical equation
be able to balance a chemical equation
recognise a molecular equation, formula equation and an ionic equation
be able to describe a chemical reaction in terms of a chemical equation
understand an acid supplies H+ ions and exists in water
recognise reactions involving dissolution, precipitation and acids
be able to complete the worksheet (if you haven’t already done so…)

10. Questions to complete for next lecture:
Chem 1001 Lecture 4
Questions to complete for next lecture:
Balance the following chemical equations:
CH4(g) + O2(g)  CO2(g) H2O(l)
CaCl AgNO3  Ca(NO3)2 + AgCl
Ag+(aq) CrO42-(aq)  Ag2CrO4(s)
Ca(s) H+(aq)  Ca2+(aq) H2(g)
Mg(OH)2(s) + H+(aq)  Mg2+(aq) H2O(l)
Classify the above equations as ‘molecular’, ‘formula’, or ‘net ionic’.
Which of the equations in question 1 represent a precipitation reaction?
Which of the equations in question 1 represent a reaction with acid?
Would it matter if you used hydrochloric acid or sulfuric acid to perform the reaction represented by equation 1d?