Chapter 3 Chem

Modern Organic Compounds

are commonly made in the lab and we find them all around us. Organic compounds are mainly made of C and H, sometimes with O, N, P, S, and trace amounts of other elements The main element that is the focus of organic chemistry is carbon.

Molecular compounds

are composed of two or more nonmetals. Generally, write the name of the element with the smallest group number first. If the two elements lie in the same group, then write the element with the greatest row number first. The prefixes given to each element indicate the number of atoms present. Prefix + Name of 1st element + Prefix + Base name of 2nd element + ide Ex: NO = Nitrogen, NO2 = nitrogen monoxide, N2O= dinitrogen monoxide, N2O4 = dinitrogen tetraoxide, N2O5 = dinitrogen pentaoxide.

Hydrates

are ionic compounds containing a specific number of water molecules associated with each formula unit. For example, the formula for epsom salts is MgSO4 • 7H2O. Its systematic name is magnesium sulfate heptahydrate. Ex. Cocl2 . 6H2O

Acids

are molecular compounds that release hydrogen ions (H+) when dissolved in water. are composed of hydrogen, usually written first in their formula, and one or more nonmetals, written second. HCl is a molecular compound that, when dissolved in water, forms H+(aq) and Cl-(aq) ions, where aqueous (aq) means dissolved in water. Dissolve many metals such as Zn, Fe, Mg; but not Au, Ag, Pt Formula generally starts with H e.g., HCl, H2SO4

Carbon Bonding

bond almost exclusively covalently. Compounds with ionic bonding C are generally inorganic. When C bonds, it forms four covalent bonds: 4 single bonds, 2 double bonds, 1 triple + 1 single, etc. Carbon is unique in that it can form limitless chains of C atoms, both straight and branched, and rings of C atoms.

Covalent bonds

bonds—which occur between two or more nonmetals—involve the sharing of electrons between two atoms. Instead the bonding atoms share some of their electrons.

Water

by contrast, is composed of water molecules that always contain two hydrogen atoms to every one oxygen atom. Water has a definite proportion of hydrogen to oxygen

Binary compounds

contain only two different elements. The names of binary ionic compounds take the following form Name of cation(metal) + base name of anion (nonmetal) +ide For example, the name for KCl consists of the name of the cation, potassium, followed by the base name of the anion, chlor, with the ending -ide. KCl is potassium chloride.

Naming of Hydrocarbons

containing only single bonds are called alkanes, while those containing double or triple bonds are alkenes and alkynes, respectively. consist of a base name and a suffix. alkane (-ane) alkene (-ene) alkyne (-yne) The base names for a number of hydrocarbons are listed here: 1 meth 2 eth 3 prop 4 but 5 pent 6 hex 7 hept 8 oct 9 non 10 dec

Functionalized Hydrocarbons

derives from the functionality or chemical character that a specific atom or group of atoms imparts to an organic compound. Even a carbon-carbon double or triple bond can justifiably be called a "functional group." A group of organic compounds with the same functional group forms a family.

Combustion of Methane

gas burns to produce carbon dioxide gas and gaseous water. Whenever something burns it combines with O2(g). CH4(g) + O2(g) ® CO2(g) + H2O(g)

molecular formula

gives the actual number of atoms of each element in a molecule of a compound.

empirical formula

gives the relative number of atoms of each element in a compound.

Hydrates prefixes

hemi = ½ mono = 1 di = 2 tri = 3 tetra = 4 penta = 5 hexa = 6 hepta = 7 octa = 8 nona= 9 deca=

Molecular Formulas for Compounds

is a multiple of the empirical formula. To determine the molecular formula you need to know the empirical formula and the molar mass of the compound. Molecular formula = (empirical formula)n, where n is a positive integer. The molar mass is a whole-number multiple of the empirical formula molar mass, the sum of the masses of all the atoms in the empirical formula:

Covalent bonds

which occur between two or more nonmetals—involve the sharing of electrons between two atoms.

Finding an Empirical Formula

. Convert the percentages to grams. a) Assume you start with 100 g of the compound. b) Skip if already grams. 2. Convert grams to moles. a) Use molar mass of each element. 3. Write a pseudoformula using moles as subscripts 4. Divide all by smallest number of moles. a) If the result is within 0.1 of a whole number, round to the whole number. 5. Multiply all mole ratios by a number to make all whole numbers. If ratio .5, multiply all by 2. if ratio .33 or .67, multiply all by 3. If ratio 0.25 or 0.75, multiply all by 4, etc. d) Skip if already whole numbers. Step 1 Write down (or calculate) as given the masses of each element present in a sample of the compound. If you are given mass percent composition, assume a 100 g sample and calculate the masses of each element from the given percentages. Given: 24.5 g N, 70.0 g O Find: empirical formula Step 2 Convert each of the masses in step 1 to moles by using the appropriate molar mass for each element as a conversion factor. 24.5 gN X 1 mol N/ 14.02g N = 1.75mol N 70.0g O X 1 mol O/ 16.00g O =4.38mol Step 3 Write down a pseudoformula for the compound using the number of moles of each element (from step 2) as subscripts. N1.75 O4.38 Step 4 Divide all the subscripts in the formula by the smallest subscript. Step 5 If the subscripts are not whole numbers, multiply all the subscripts by a small whole number (see table) to get whole-number subscripts.

Composition of Compounds

A chemical formula, in combination with the molar masses of its constituent elements, indicates the relative quantities of each element in a compound, which is extremely useful information

Combustion Analysis

A common technique for analyzing compounds is to burn a known mass of compound and weigh the amounts of product made. This is generally used for organic compounds containing C, H, O. By knowing the mass of the product and composition of constituent element in the product, the original amount of constituent element can be determined. All the original C forms CO2, the original H forms H2O, and the original mass of O is found by subtraction. Once the masses of all the constituent elements in the original compound have been determined, the empirical formula can be found.

Compound form more than one cation

For these types of metals, the name of the cation is followed by a roman numeral (in parentheses) that indicates the charge of the metal in that particular compound. For example, we distinguish between Fe2+ and Fe3+ as follows: Fe2+ Iron(II) Fe3+ Iron(III) Name of the cation (metal) +(Charge of cation in roman number)+Base name of the anion (nonmetal) +ide

naming binary acids

Hydro + base name of nonmetal + ic +acid Name HC2H3O2(aq). The oxyanion is acetate, which ends in -ate; therefore, the name of the acid is acetic acid. HC2H3O2 (aq) acetic acid

Naming oxyacids

If polyatomic ion name ends in -ate, then change ending to -ic suffix. If polyatomic ion name ends in -ite, then change ending to -ous suffix. Write word acid at the end of all names. Oxyanions ending with -ate = base name of oxyanion + -ic + acid Oxyanions ending with - ite = base name of oxyanion + -ous + acid When name ends in acid, formulas starts with H. Write formulas as if ionic, even though it is molecular. Hydro- prefix means it is binary acid; no prefix means it is an oxyacid. For oxyacid if ending is -ic, polyatomic ion ends in -ate. if ending is -ous, polyatomic ion ends in -ous

Oxyanions

Most polyatomic ions are oxyanions, anions containing oxygen and another element. Notice that when a series of oxyanions contains different numbers of oxygen atoms, they are named according to the number of oxygen atoms in the ion. If there are two ions in the series, the one with more oxygen atoms has the ending -ate, and the one with fewer has the ending -ite. For example, NO3- is nitrate SO42- is sulfate NO2- is nitrite SO32- is sulfite If there are more than two ions in the series then the prefixes hypo-, meaning less than, and per-, meaning more than, are used. ClO- hypochlorite BrO- hypobromite ClO2- chlorite BrO2- bromite ClO3- chlorate BrO3- bromate ClO4- perchlorate BrO4- perbromate

Hydrocarbons

Organic compounds can be categorizing into types: hydrocarbons and functionalized hydrocarbons. are organic compounds that contain only carbon and hydrogen. ___________________ compose common fuels such as oil, gasoline, liquid propane gas, and natural gas.

Chemical Reactions

Reactions involve chemical changes in matter resulting in new substances. Reactions involve rearrangement and exchange of atoms to produce new molecules. Elements are not transmuted during a reaction. Reactans ---> Products

Chemical Equations

Shorthand way of describing a reaction Provide information about the reaction Formulas of reactants and products States of reactants and products Relative numbers of reactant and product molecules that are required Can be used to determine weights of reactants used and products that can be made

Molar Mass of Compounds

The relative masses of molecules can be calculated from atomic masses: formula mass = 1 molecule of H2O = 2(1.01 amu H) + 16.00 amu O = 18.02 amu

Type II Ionic Compounds

The second type of ionic compound contains a metal with a charge that can differ in different compounds. The metals in this second type of ionic compound can form more than one kind of cation (depending on the compound). Its charge must therefore be specified for a given compound. Iron, for instance, forms a 2+ cation in some of its compounds and a 3+ cation in others. Metals of this type are often transition metals. FeSO4 Here iron is +2 cation (Fe2+). Fe2(SO4)3 Here iron is +3 cation (Fe3+). Cu2O Here copper is +1 cation (Cu+). CuO Here copper is +2 cation (Cu2+). Some main group metals, such as Pb, Tl, and Sn, form more than one type of cation.

Combustion of Methane, Balanced

To show the reaction obeys the Law of Conservation of Mass the equation must be balanced. We adjust the numbers of molecules so there are equal numbers of atoms of each element on both sides of the arrow.

Polyatomic Ions

We name ionic compounds that contain a ________________ in the same way as other ionic compounds, except that we use the name of the __________________ whenever it occurs. For example, NaNO2 is named according to its cation, Na+, sodium, and its polyatomic anion, NO2-, nitrite. Hence, NaNO2 is sodium nitrite.

NH4OH

Both ionic and molecular because charges cancel but both are non-metals

Acid Rain

Certain pollutants—such as NO, NO2, SO2, SO3—form acids when mixed with water, resulting in acidic rainwater. can fall or flow into lakes and streams, making these bodies of water more acidic.

Organic Compounds

Early chemists divided compounds into two types: organic and inorganic. Compounds from living things were called organic; compounds from the nonliving environment were called inorganic. Organic compounds are easily decomposed and could not be made in the lab. Inorganic compounds are very difficult to decompose, but are able to be synthesized

hydrogen

oxygen mixture can have any proportions of hydrogen and oxygen gas.

Chemical bonds

result from the attractions between the charged particles (the electrons and protons) that compose atoms. Compounds are composed of atoms held together by ________________

structural formula

uses lines to represent covalent bonds and shows how atoms in a molecule are connected or bonded to each other