Types of Chemical Reactions

5 types of reactions

Summary

• Today you will perform experiments that include each of the major types of chemical reaction

• These are– single replacement– double displacement – combustion– decomposition– combustion

Single Replacement

• In this type of reaction an element in a compound is replaced by another

Ca + ZnSO4 Zn + CaSO4

Cl2 + 2NaBr Br2 + 2NaCl

Double Replacement

• Two ionics swap partners ….

CaCl2 + ZnSO4 CaSO4 + ZnCl2

Combination Reaction

• This happens when 2 substances become 1 substance

• Or when 2 compounds make a larger compound

Ca + Cl2 CaCl2

CaO + H2O Ca(OH)2

Decomposition Reaction

• This is the opposite of a combination reaction it is when a substance falls apart into other substances

Ca(OH)2 CaO + H2O

Combustion Reaction

• AKA burning, when a substance combines with oxygen

• Often water and carbon dioxide are produced

CH4 + 2O2 CO2 + 2H2O

Oxidation-Reduction Reactions

• Some of the 5 types of reaction can be classified of Reduction-Oxidation (Redox) reactions

• Something loses electrons (is oxidized)• And something receives the electrons (is reduced)• All single replacement reactions are redox reactions

Ca + (Zn2+)(SO42-) Zn + (Ca2+)(SO4

2-)

Ca + ZnSO4 Zn + CaSO4

Ca Ca2+ + 2e- Zn2+ + 2e- ZnCa loses electrons and is oxidized to Ca2+ Zn2+ gains electrons and is oxidized to Zn

Oxidation-Reduction Reactions

• All combustion reactions are redox reactions• Its harder to see because the elements don’t have

charges to help us see• Oxidation is the gain of oxygen (or loss of H)• Reduction is the loss of oxygen (or gain of H)

C in CH4 gains O it is oxidized O in H2O has gain H and has been reduced, or the O2 has lost O and is reduced

CH4 + 2O2 CO2 + 2H2O

Evidence of a Chemical Reaction

• Reactions in this experiment are conducted in water (solvent)

• Here are indicators that a reaction has occurred– Formation of a Gas– A Precipitate Forms– Heat is Produced– A Color Change in Seen (unreliable)

Balancing Reactions

• Three Rules to Balancing Equations1. Write correct Formulae of reactants and products2. Use Stoichiometric coefficients in front of each

compound so that the number of atoms of each type on the left hand side are the same as on the right

3. Use the smallest whole numbers possible as coefficients

The Reactions

• 1 mL 0.1 M CaCl2 + 1 mL 0.1 M Na3PO4

• Heat 0.5 g of table sugar in a disposable test tube over a bunsen– what is the liquid forming on the side of the test tube?

• 3 mL H2O2 and a spatula tip of MnO2 and heat– a gas is evolved O2 – you can prove by adding a glowing

splint• 3 mL of 3 M HCl and a small piece of Zinc– after about 30 s bring a lighted splint to the mouth of the

tube

The Reactions• 1 mL 3M HCl + 1 mL 1.0 M Na2CO3

– what is the gas? Place a lighted splint in the test tube

• 2 mL 3M H2SO4 in a test tube with 2 drops of phenolphthalein then add 5 mL of 3M NaOH– color changes? phenolphthalein is pink when the water is

alkaline and clear when acid – Feel the bottom of the tube is the reaction mixture warm

• 2mL of 0.05 M AgNO3 and a small piece of Cu in a test tube– Careful AgNO3 causes chemical burns to clothes and skin

• 0.5 g CuSO4.H2O and heat in a test tube