Matthew Falcione Period 5 Types of Chemical Reactions React ions Discussion In chemical reactions, the rearrangement of the molecular or ionic structure of a substance occurs. The rearrangement of the molecules either absorbs energy energy or releases energy. A reaction that releases energy is called exothermic, while w hile a reaction that absorbs energy and cools down is c alled an st
endothermic. This occurs because the 1 Law of Thermodynamics states energy cannot be created or destroyed only changed. Energy is transferred or transformed from one state to another. The total amount of energy in a closed system never changes; therefore the total amount of energy in the reactants is equal to the total t otal amount of energy of the products. Among the five types of chemical r eactions, combination, decomposition, single-replacement, doublereplacement, and combustion, three were observed by by doing various chemical experiments. Those three were single-replacement, double-replacement, and combustion. In the first experiment Fe was added to CUSO4. This reaction was an example example of a single- replacement reaction. The products were were FeSO4 and Cu. The iron, which was black, black, was replaced by copper, which was orange. This color change change is an occurrence during a chemical reaction. In the second experiment Pb(NO3)2 was added to KI, which resulted in PBI2 and 2KNO3. This is an example of a double-replacement reaction. When the reaction occurred a precipitate, PBI2, was formed. In the third third reaction Mg was added to HCl. HCl. The products were MgCl2 and H2. This was an example example of a single replacement reaction. In the fourth experiment H2O2, from the Mg and HCl reaction, was introduced to heat to test if it was in fact H2 that had formed. This resulted in a popping noise, which is a characteristic characteristic of burning H2. This is an example of a combustion reaction. Every reaction can be characterized by their reactants and products. A combination reaction has has a single product. A decomposition reaction reaction has a single reactant. In a single-replacement single-replacement reaction, one element displaces another element from an aqueous solution of a compound, to form a new compound and a free element. In a double-replacement reaction, reaction, two new compounds are formed when aqueous solutions of two ionic compounds are mixed. One of the new ly formed compounds is a precipitate, a gas, or a molecular compound. compound. In a combustion reaction, reaction, O2 reacts with another chemical to produce an oxide and to generate heat and light. When O2 reacts with a hydrocarbon, the products of the reaction are CO2 and H2O. Each one of these reactions has a limiting reactant, which is the substance that limits the amount of product that can be formed, meaning the reaction will stop when all of the reactant is used. Each type of reaction has different changes in the molecules and the bonds that hold them together. In a synthesis reaction two or more chemical compounds combine to form a more complex product. In a decomposition reaction a compound is broken into two or more simpler molecules. A substitution or single replacement reaction is characterized by one element being displaced from a compound by another element. In a double displacement reaction two compounds compounds exchange bonds or ions in order to
form different compounds. A combustion reaction is a reaction which requires a combustible material, usually a hydrocarbon, to combine with an oxidizer to for m CO2 and H20. Combustion generates heat, which means it is an exothermic reaction. A chemical reaction is often noted by a color change, production of a gas, or the formation of a precipitate. A precipitate is a solid that forms out of solution because that solid is insoluble in that solution.
References 1st Law of Thermodynamics. (n.d.). Ohio State University. Retrieved May 9, 2014, from http://chemistry.osu.edu/~woodward/ch121/ch5_law.htm First Law of Thermodynamics. (n.d.). Hyperphysics. Retrieved May 9, 2014, from http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/firlaw.html Law of Conservation. (n.d.). Energy Education. Retrieved May 9, 2014, from http://www.energyeducation.tx.gov/energy/section_1/topics/law_of_conservation/ Precipitation Reactions. (n.d.). Indiana University Northwest . Retrieved May 9, 2014, from http://www.iun.edu/~cpanhd/C101webnotes/chemical%20reactions/precipitation.html Stoichiometry Limiting Reactant. (n.d.). Texas A&M University. Retrieved May 9, 2014, from http://www.chem.tamu.edu/class/majors/tutorialnotefiles/limiting.htm The Six Types of Chemical Reaction. (n.d.). Mr. Guch Brinkster . Retrieved May 9, 2014, from http://misterguch.brinkster.net/6typesofchemicalrxn.html