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 + ZnSO 4  Zn + CaSO 4 Cl 2 + 2NaBr  Br 2 + 2NaCl

Double Replacement Two ionics swap partners …. CaCl 2 + ZnSO 4  CaSO 4 + ZnCl 2

Combination Reaction This happens when 2 substances become 1 substance Or when 2 compounds make a larger compound Ca + Cl 2  CaCl 2 CaO + H 2 O  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 + H 2 O

Combustion Reaction AKA burning, when a substance combines with oxygen Often water and carbon dioxide are produced CH 4 + 2O 2  CO 2 + 2H 2 O

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 + (Zn 2+ )(SO 4 2- )  Zn + (Ca 2+ )(SO 4 2- ) Ca + ZnSO 4  Zn + CaSO 4 Ca  Ca e - Zn e -  Zn Ca loses electrons and is oxidized to Ca 2+ Zn 2+ 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 CH 4 gains O it is oxidized O in H 2 O has gain H and has been reduced, or the O 2 has lost O and is reduced CH 4 + 2O 2  CO 2 + 2H 2 O

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 Equations 1.Write correct Formulae of reactants and products 2.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 CaCl mL 0.1 M Na 3 PO 4 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 H 2 O 2 and a spatula tip of MnO 2 and heat – a gas is evolved O 2 – 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 Na 2 CO 3 – what is the gas? Place a lighted splint in the test tube 2 mL 3M H 2 SO 4 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 AgNO 3 and a small piece of Cu in a test tube – Careful AgNO 3 causes chemical burns to clothes and skin 0.5 g CuSO 4.H 2 O and heat in a test tube