Chemical Reactions By: Margaret Bambling And Alex Nahum

Why do reactions take place? They occur whenever bonds are formed or broken between molecules Chemical reactions occur when one or more reactants change into one or more products

Chemical equations Is a quick shorthand notation to convey as much information as possible about what happens in a chemical reaction

Writing equations Reactants on the left: present at start of reaction Products on the right: produced in chemical reaction Separated by an arrow: arrow reading as yields –Ex. Iron + oxygen iron (III) oxide Reactant Product

What is a balance chemical equation A balanced equation is when each side of the equation has the same number of atoms of each element and mass is conserved

Why Balance chemical equations You have to balance equations for the reasoning of the law of conservation of matter Can not destroy, or create matter

How do you balance equations Equation has to indicate the quantity of the reactants needed to make the product To show quantity write coefficients in front of the formulas in equation Use coefficients to balance equation so that it obeys the law of conservation

Example of balancing equations Before: NaCl Na+Cl2 Chlorine is diatomic and always bonds into Cl2 when bonding by itself After: 2NaCl 2Na+cl2 Added 2 in front of Na to balance out the number of elements

Synthesis Reaction Two or more substance react to form a single new substance Written example : A+X = AX +

Decomposition Reaction Change in which a single compound breaks down into two or more simpler products Written example: BX A + X +

Single Displacement Reaction Change in which one element replaces a second element in a compound A metal replaces a metal and a nonmetal replaces a nonmetal A + BX AX + B ++

Double displacement Reaction Change involving an exchange of positive ions between two compounds AB + XY AY + XB Take place in aqueous solution and often produce a precipitate, gas or a molecular compound + +

Precipitates Solid deposit from a solution Whether a precipitate forms depend on both the solutes concentrations, and its saturation solubility at the specified temperature, as well as the maximum amount a substance can be dissolved into a given solvent

Precipitates Cont… Forms when two ionic compounds are mixed, that are both soluble, but form an insoluble compound when mixed If AB and CD are both soluble, and A+ and B- are soluble, and C+ and D- are also, but when mixed compound A+D- is insoluble

Combustion Reaction Change in which an element or compound reacts with oxygen producing energy in the form of heat and light Always involves oxygen as a reactant Releases a large amount of energy as heat CXHX + O2 CO2 + H2O 2 C8H O > 16 CO H2O