Reactions

Seven Diatomic Elements (Super Seven) never appear alone in nature. They are chemically combined in compounds or with themselves. These include hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine. H2, N2, O2, F2­, Cl2, Br2, I2­

IV. Types of Chemical Reactions Combination or Synthesis A reaction in which two or more substance combine to form a single product Examples:

2. Examples: 2H2 + O2  2 H2O 4Al + 3O2  2Al2O3 Ca + Cl2  CaCl2 2KCl + 3O2  2KClO3 Notice that in each example, a compound is formed from elements or smaller compounds. This may be represented by the following general equation: A + B  AB

B. Decomposition Reaction A reaction in which a compound is broken down into simpler substances such as elements or smaller compounds Examples

2. Examples 2HgO ∆ 2Hg + O2 2H2O 𝑒𝑙𝑒𝑐𝑡𝑟𝑐𝑖𝑡𝑦 2H2 + O2 2 KClO3 𝐶𝑎𝑡𝑎𝑙𝑦𝑠𝑡 2KCl + 3O2 Decomposition reactions are generally the opposite of composition reactions. Such a reaction may be represented by the following general equation: AB  A + B

C. Single Replacement Reaction A reaction in which one element reacts with a compound to form a different element and another compound Examples

2. Examples Cu + 2AgNO3  Ag + Cu(NO3)2 Zn + Cu(NO3)2  Cu + Zn(NO3)2 Mg + 2HCl  H2 + ZnCl2 These reactions occur according to the activity series of metals. Elements on the top of the list may replace elements below them in a chemical reaction. For the Halogens, elements may replace those below them in the group. The general equation for a single replacement reactions looks like: A + BC  B + AC

D. Double Replacement Reactions A reaction in which the metals (or cations) present in two compounds changes places to form two new compounds. Examples

2. Examples AgNO3 + NaCl  AgCl + NaNO3 NaOH + HCl  NaCl + H2O Ba(NO3)2 + Na2SO4  BaSO4 + 2NaNO3 The general equation for a double replacement reactions is: AB + CD  AD + CB These reactions often use the solubility rules to predict precipitate formation.

E. Combustion Reaction A reaction in which oxygen reacts with another substance usually producing heat and light. (We will be dealing primarily with the combustion of hydrocarbon fuels) There are two kinds of combustions: complete combustion and incomplete combustion

Examples CxHy + O2  CO2 + H2O CxHy + O2  CO + C + H2O Elemental carbon or soot, among other things may be formed during incomplete combustion.

F. Oxidation – Reduction Reactions A reaction in which the oxidation number of an element changes. Think of a number line. If the oxidation number moves to the right on the number line (becomes less negative or more positive) the element is oxidized. If the oxidation number moves to the left on the number line (becomes more negative or less positive) the element is reduced. To calculate the oxidation of the element, use the charge of the element or polyatomic ion to determine the charge of the metal in each substance. Elements in their natural state have an oxidation number of zero.

4. Examples Ag + NaCl  AgCl + Na Al + Cu(NO3)2  Cu + Al(NO3)3 For this course, we will concentrate on oxidation-reduction reactions that are also single replacement reactions, but others do exist.

Na3PO4 + BaCl2  Ba3(PO4)2 + NaCl MgCl2  Mg + Cl2 What type of chemical reaction is represented by the following equations? Ca + BaO  Ba + CaO 2C3H6 + 9O2 6CO2 + 6H2O Ca + O2  CaO Na3PO4 + BaCl2  Ba3(PO4)2 + NaCl MgCl2  Mg + Cl2 SR CB S DR D

Nuclear Reactions A reaction in which nucleotides (particles) react during nuclear fusion or fission. Fusion – is the combination of two smaller nucleotides for form a larger, more massive particle. This is what happens in our sun. Fission – is the splitting of a large, unstable nucleotide into smaller particles. This occurs in nuclear reactors.

The particles involved include the following Alpha particles, a, look like helium ions: 𝟐 𝟒 𝑯𝒆 𝟐+ Beta particles, b, look like electrons: −𝟏 𝟎 𝒆 Positrons look like positive beta particles: +𝟏 𝟎 𝒆 Neutrons are just neutrons: 𝟎 𝟏 𝒏 Protons are often written as hydrogen ions: 𝟏 𝟏 𝑯 + Gamma Rays – really a form of radiation that accompanies many nuclear reactions: 0 0 𝛾 or just g

To balance a nuclear reaction, make sure the total mass numbers on each side of the reaction are equal and the total atomic numbers on each side are equal. Examples 3 6 Li + 1 2 H → 2 4 He + 6 + 2 = 4 + x x=4 3 + 1 = 2 + y y = 2 𝟐 𝟒 𝐇𝐞

6 14 𝐶 + 1 1 𝐻 → 0 1 𝑛 + _____ 92 238 𝑈 → 234 𝑇ℎ + _____ 6 14 𝐶 + 1 1 𝐻 → 0 1 𝑛 + _____ 92 238 𝑈 → 234 𝑇ℎ + _____ 234 𝑇ℎ → 234 𝑃𝑎 + _____ 𝟕 𝟏𝟒 𝐍

7. Radiation Alpha radiation is the least penetrating. It can be stopped by a piece of paper. This is because of the size of the particles. Beta radiation is moderately penetrating. Aluminum foil is thick enough to stop beta radiation. Gamma radiation is the most penetrating because it is a form of electromagnetic radiation. Layers of concrete and lead are needed to stop gamma radiation.