Chemistry 1405 - Exam 3 - Chapters 4 and 5

Why is it necessary for a chemical equation to be balanced before it can be used to construct conversion factors?

A balanced chemical equation is necessary so one can construct the proper stoichiometric ratios.

Anaerobic Metabolism

A biochemical process that takes place in the absence of oxygen.

Molecular Formulas

A chemical formula for a covalent compound. Typically, a molecular formula begins with the nonmetal that is closest to the lower left corner of the periodic table, except that hydrogen is almost never written first (H2O is the prominent exception). Then the other nonmetal symbols are listed.

Combustion Reaction

A chemical reaction accompanied by the production of light and/or heat, typically a vigorous reaction because of combination with oxygen.

Decomposition Reaction

A chemical reaction in which a single substance is converted into two or more products.

Oxidation-Reduction Reactions

A chemical reaction in which electrons are transferred from one atom to another. Also called a redox reaction.

Combination (Composition) Reaction

A chemical reaction that makes a single substance from two or more reactants.

What is the difference between a combination reaction and a combustion reaction?

A combination reaction produces a certain substance; a combustion reaction is a vigorous reaction, usually a combination with oxygen, that is accompanied by the production of light and/or heat.

Organic Compound

A compound containing carbon atoms.

Single Bond

A covalent bond formed by a single pair of electrons.

Nonpolar Covalent Bond

A covalent bond with a balanced electron distribution across the bond.

Polar Covalent Bond

A covalent bond with an unbalanced electron distribution across the bond.

Molecule

A discrete group of atoms connected by covalent bonds.

Carboxyl group

A functional group that contains a carbon-oxygen double bond and an OH group also attached to the same carbon atom.

Alkenes

A hydrocarbon with one or more carbon-carbon double bonds. Note that the names of alkenes have the same stem as the alkane with the same number of carbon atoms in its chain but have the ending -ene. Thus, ethene is an alkene with two carbon atoms per molecule, and propene is a compound with three carbon atoms and one double bond.

Alkanes (Saturated Hydrocarbons)

A hydrocarbon with only single covalent bonds and existing as a chain of carbon atoms also bonded to hydrogen atoms. These names consist of a stem that indicates the number of carbon atoms in the chain plus the ending -ane. The stem meth- means one carbon atom, so methane is an alkane with one carbon atom. Similarly, the stem eth- means two carbon atoms; ethane is an alkane with two carbon atoms. Continuing, the stem prop- means three carbon atoms, so propane is an alkane with three carbon atoms.

Lewis Dot Diagram

A method for representing an atom's valence electrons using dots around the element symbol.

Coefficient

A number that gives the number of molecules of a substance in a balanced chemical equation.

Balanced

A property of a chemical equation when there are the same number of atoms of each element in the reactants and products.

Electronegativity

A relative measure of how strongly an atom attracts electrons when it forms a covalent bond.

Chemical Reaction

A representation of a chemical change.

Oxidizing Agent

A species that causes oxidation, which is itself reduced.

Reducing Agent

A species that causes reduction, which is itself oxidized

Functional Groups

A specific structural arrangement of atoms or bonds that imparts a characteristic chemical reactivity to a molecule.

Antioxidants

A substance in foods that acts as a reducing agent

Reactants

A substance on the left side of the arrow in a chemical equation.

Products

A substance on the right side of the arrow in a chemical equation.

Covalent bond

A type of strong chemical bond in which two nonmetal atoms share one or more pairs of valence electrons.

Electronegativity and Bond Polarity

Although we defined covalent bonding as electron sharing, the electrons in a covalent bond are not always shared equally by the two bonded atoms. Unless the bond connects two atoms of the same element, there will always be one atom that attracts the electrons in the bond more strongly than the other atom does. When such an imbalance occurs, there is a resulting buildup of some negative charge (called a partial negative charge and designated δ−) on one side of the bond and some positive charge (designated δ+) on the other side of the bond. A covalent bond that has an unequal sharing of electrons, as in part (b) of is called a polar covalent bond.

Chemical Equation

An abbreviated way of using symbols to represent a chemical change.

Carboxylic acids

An organic compound that has a carboxyl functional group.

Alcohol

An organic compound with an OH functional group. If an OH group (also called a hydroxyl group) is substituted for a hydrogen atom in a hydrocarbon molecule, the compound is an alcohol. Alcohols are named using the parent hydrocarbon name but with the final -e dropped and the suffix -ol attached. The two simplest alcohols are methanol and ethanol.

How Many Covalent Bonds Are Formed?

Atoms may form multiple covalent bonds - that is, share not just one pair of electrons but two or more pairs. Atoms of different elements will form either one, two, three or four covalent bonds with other atoms. There is a quick way to work out how many covalent bonds an element will form. The number of covalent bonds is equal to eight minus the group number. Hydrogen forms one covalent bond. The noble gases in Group 0 do not form any.

Nonbonding Pairs (Or Lone Pairs)

Electron pair that does not participate in covalent bonds.

What does the electronegativity of an atom indicate?

Electronegativity is a qualitative measure of how much an atom attracts electrons in a covalent bond.

Law Of Conservation Of Matter

In any given system that is closed to the transfer of matter (in and out), the amount of matter in the system stays constant. A concise way of expressing this law is to say that the amount of matter in a system is conserved

Bond length II

Other covalent bonds also have known bond lengths, which are dependent on both the identities of the atoms in the bond and whether the bonds are single, double, or triple bonds. Bond Length (×10−12 m) H-H 74 H-C 110 H-N 100 H-O 97 H-I 161 C-N 147 C-O 143 C-C 154 C=C 134 C≡C 120 C-N 147 C=N 128 C≡N 116 C-O 143 C=O 120 C≡O 113 N-N 145 N=N 123 N≡N 110 O-O 145 O=O 121

Explain how stoichiometric ratios are constructed from a chemical equation.

Stoichiometric ratios are made using the coefficients of the substances in the balanced chemical equation.

Respiration

The biochemical process by which the oxygen we inhale oxidizes foodstuffs to carbon dioxide and water.

Bond Length

The distance between two nuclei in a covalent bond. Bond length represents a balance between several forces: the attractions between oppositely charged electrons and nuclei, the repulsion between two negatively charged electrons, and the repulsion between two positively charged nuclei. If the nuclei were closer together, they would repel each other more strongly; if the nuclei were farther apart, there would be less attraction between the positive and negative particles.

Naming binary (two-element) covalent compounds

The first element in the formula is simply listed using the name of the element. The second element is named by taking the stem of the element name and adding the suffix -ide. A system of numerical prefixes is used to specify the number of atoms in a molecule. 1 mono-* 2 di- 3 tri- 4 tetra- 5 penta- 6 hexa- 7 hepta- 8 octa- 9 nona- 10 deca-

Reduction

The gain of electrons by an atom.

Valence Shell Electron Pair Repulsion (VSEPR)

The general concept that estimates the shape of a simple molecule. The shape of a molecule is determined by the fact that covalent bonds, which are composed of negatively charged electrons, tend to repel one another. For example, the two covalent bonds in BeCl2 stay as far from each other as possible, ending up 180° apart from each other. The result is a linear molecule.

Oxidation

The loss of electrons by an atom.

Molecular Mass

The mass of a molecule, which is the sum of the masses of its atoms.

How do you determine the molecular mass of a covalent compound?

The molecular mass is the sum of the masses of the atoms in the formula.

Photosynthesis

The process by which plants use solar energy to convert carbon dioxide and water to glucose.

How do you determine the shape of a molecule?

The shape of a molecule is determined by the position of the atoms, which in turn is determined by the repulsion of the bonded and lone electron pairs around the central atom.

Hydrocarbons

The simplest organic compound, composed of carbon and hydrogen atoms only.

Organic Chemistry

The study of the chemistry of carbon compounds. Carbon is singled out because it has a chemical diversity unrivaled by any other chemical element. Its diversity is based on the following: 1. Carbon atoms bond reasonably strongly with other carbon atoms. 2. Carbon atoms bond reasonably strongly with atoms of other elements. 3. Carbon atoms make a large number of covalent bonds (four).

Stoichiometry

The study of the numerical relationships between the reactants and the products in a balanced chemical equation.

Bonding Pair Of Electrons

The two electrons that join atoms in a covalent bond.

Triple Bonds

Three pairs of electrons being shared by two atoms in a molecule.

Double Bond

Two pairs of electrons being shared by two atoms in a molecule.

Physical Properties and Polarity

When a molecule's bonds are polar, the molecule as a whole can display an uneven distribution of charge, depending on how the individual bonds are oriented. For example, the orientation of the two O-H bonds in a water molecule (Figure 4.5 "Physical Properties and Polarity") is bent: one end of the molecule has a partial positive charge, and the other end has a partial negative charge. In short, the molecule itself is polar.

What is the name for the distance between two atoms in a covalent bond?

bond length

Formulas and Molecular Models of the Two Simplest Alkenes

ethene, C2H4 propene, C3H6

Formulas and Molecular Models of the Two Simplest Alkynes

ethyne, C2H2 propyne, C3H4

Alkynes

hydrocarbons with a carbon-carbon triple bond (denoted C≡C) as part of their carbon skeleton. he names for alkynes have the same stems as for alkanes but with the ending -yne.

Formulas and Molecular Models of the Three Simplest Alkanes

methane, CH4 ethane, C2H6 propane, C3H8

What type of bond is formed between two atoms if the difference in electronegativities is small? Medium? Large?

nonpolar; polar; ionic

The Pauling Scale

numerical scale for rating electronegativity. The polarity of a covalent bond can be judged by determining the difference in the electronegativities of the two atoms making the bond. The greater the difference in electronegativities, the greater the imbalance of electron sharing in the bond. 0.4 or less = nonpolar 0.4 - 1.7 = polar 1.8 or more = ionic