Types of Reactions PDF

Types of Reactions Objectives: TO study about different types of reactions, learn the differences between oxidation & reduction reactions, exothermic and endothermic reactions and balancing equations.  What is a Chemical Reaction? It is a chemical change in which atoms and mole...

Types of Reactions Objectives: TO study about different types of reactions, learn the differences between oxidation & reduction reactions, exothermic and endothermic reactions and balancing equations.  What is a Chemical Reaction? It is a chemical change in which atoms and molecules rearrange themselves to give a new product. BEFORE AFTER 2H2 gas 2H2O liquid and O2 gas  Parts of a Chemical Reaction Reactants Products Reactants (left side): Substances that participate in a chemical reaction. (bonds are broken). Products (right side): New substances that are formed in a chemical reaction.(new bonds are formed). The arrow () is read as “yields” or product.  Other symbols in chemical reactions (s) = solid,(l) = liquid,(g) = gas (aq.) = aqueous solution (the substance is dissolved in H2O) Dil.= dilute (more water less solute) Conc.=concentrated (less water more solute) “+” separates two or more reactants or products. Precipitate =  Evidence for a Chemical Reaction 1) Evolution of light or heat.  Evidence for a Chemical Reaction 2) Temperature change (increase or decrease) to the surroundings.  Word Equations Statements that indicate the reactants and products in a chemical reaction. Ex. Iron (s) + chlorine (g)  iron (III) chloride (s) This is read as: “Solid iron and chlorine gas react (combine) to produce solid iron (III) chloride” Oxidation and Reduction Reducing agent : A substance which can be used to remove oxygen from a compound. Oxidising agent: A substance which has the ability to oxidise other substance or accept electrons. Examples of oxidation reactions Zinc + oxygen → zinc oxide Sodium + oxygen → sodium oxide Calcium + oxygen → calcium oxide Carbon + oxygen → carbon mono- oxide /carbon- dioxide Nitrogen + oxygen → nitrogen mono oxide / nitrogen -di oxide Examples of reduction reactions Iron oxide + carbon → iron + carbon dioxide  heat Calcium carbonate → Calcium oxide + carbon-di-oxide heat Mercury oxide → Mercury + Oxygen  electricity Water → oxygen + hydrogen l g g electricity Sodium chloride(aq) → sodium + s chlorineg Decomposition by Light  light Silver Chloride → Silver + chlorine light Silver Bromide → Silver + bromine Hydrochloric acid + calcium carbonate → calcium chloride +carbon di oxide↑+ water Hydrochloric acid + Sodium hydroxide → Sodium chloride + Water Hydrochloric acid + Calcium oxide → Calcium Chloride + Water Lead nitrate + Potassium iodide → lead iodide ↓+ potassium nitrate Solution solution solid solution Sodium sulphate+ barium nitrate→ sodium nitrate + barium sulphate ↓ Solution solution solution solid Chromium oxide + aluminium → Chromium + aluminium oxide Copper sulphate+ Iron → Iron sulphate + copper  Conservation of Mass During a chemical reaction, atoms are neither created nor destroyed (Conservation of Mass). Hydrogen and oxygen gas react to form water: H2 (g) + O2 (g) H2O (l)  Conservation of Mass H2 (g) + O2 (g) H2O (l) What is wrong with this equation above? Doesn’t it appear that one oxygen atom “went missing”? According to conservation of mass, the proper way to write this reaction is: 2H2 (g) + O2 (g) 2H2O (l) The red coefficients represent the number of molecules of each reactant or product. Coefficient is multiplied with the numbers written in subscript( bottom number )  Counting Atoms SnO2 + 2H2 → Sn + 2H2O SUBSCRIPT COEFFICIENT  Warm-Up 2Ca3(PO4)2 + 6 SiO2 + 10C 6 CaSiO3 + P4 +10CO Atom # Atoms on Left # Atoms on Right Side Side Ca 6 6 P 4 4 O 28 (8x2)=16 6x3=18+10=28 (6x2)=12 16+12=28 Si 6 6 C 10 10  Rules for Balancing Chemical Reactions __2H2 + __ O2 _2H2O Balancing is about finding the right coefficients!  Rules for Balancing Chemical Reactions 1) You can change the coefficients, but NEVER the subscripts! _2_H2 + _1_ O2 _2_H2O coefficient coefficient subscript subscript coefficient