Basics Chemistry Ch. 3 Note - Summary PDF

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Summary of Ch. 3 of a molecular approach textbook...

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64Ch. 3 Molecular compound   

Molecules are formed when atoms bond by sharing electrons. Several elements are found in nature as diatomic molecules Molecules comprised of more than 1 element are molecular compounds

Ions     

Neutral atom/molecule loses/gains electrons it becomes an ion Cation – positive are formed when they lose an electron Anions – negative ions are formed when they gain an electron Mental tend to form cations while nonmetals (cept noble gases) tend to form anions Sometimes a group of atoms will gain/lose electrons. These are polyatomic ions. They are more common than cations. o Ex. Sulfate – polyatomic anion o Ex. Ammonium – polyatomic cation

Ionic compounds  

Generally formed between metals and nonmetals Electrons are transferred from metal to nonmetal. The oppositely charged ions attract each other. Empirical formulas are typically written for ionic compounds

Structural formulas/3D models

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Structural formulas – show order in which atoms are attached but not in 3D Perspective drawing, ball and stick models, space filling models – 3D order of atoms in compounds

Chemical formula   

Represents molecule using symbols for elements and subscripts to indicate the number of atoms of each element in a molecule Empirical formulas – give numbers of atoms in each element in a compound Molecular formulas – give number of atoms of each element in a molecule

Writing formulas for ionic compounds

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Compounds are electrically neutral, formula for ionic compound can be contrived this way: o NG: 3*2=6, N: 2*-3=-6/ -6+6=0 = neutral o Charge on the cation becomes subscript for anions and vice versa o If subscript is not in the lowest whole number ratio, divides them by greatest common factor o Ex. Magnesium chloride: MgCl2, silver I fluoride: AGF, aluminum selenium: Al2Se3. Copper hydride (because it is hydride it is -1): CuH2, Colbalt (II) Nitrate: Co(No3)2, calcium phosphate: Ca3(PO3)2, sodium bicarbonate: Na(HCO2), titanium (IV) oxide: Ti2O4 => TiO2

Naming ionic compounds   

System of naming compounds – chemical nomenclature Write the name of cation, have more than 1 possible charge, write the charge numeral in parentheses. If anion is an element, change its ending to –ide, if the anion is polyatomic ion, simple write the name of the polyatomic ion o Kl – potassium iodide

o RbCl –Rubidium chloride o CuCl – Copper (I) chloride (copper is one of those that have multiple charges) o CrO3 – Chromium (VI) oxide  3 oxygens * -2 charge = -6 so chromium must be VI o SrCo3 – Strontium carbonate  Sr = +2 while Co3 = -2 o (NH4)No3 – Ammonium (IV) nitrate  No3 = -1, nh4 = +1 o HCl – Hydrogen chloride  Hydrogen = +1, chlorine = -1 o KOH – Potassium Hydroxide  Potassium = +1 , hydroxide = -1 Patterns in oxyanion nomenclature

Mineral acid nomenclature   

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Mineral acids are compounds of H+ ion with inorganic anions Usually second to last column If the anion in the acid ends in –ide, change the ending to –ic acid and add prefix hydroo HCl: hydrochloric acid o HBr: hydrobromic acid o Hl: hydroiodic acid If anion ends in –ite, change the ending to –ous acid o HClO: hypochlorous acid o HClO2: chlorous acid If anion ends in –ate, change the ending to –ic acic o HClO3: chloric acid o HClO4: perchloric acid

Nomenclature binary molecular compounds:

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Name of the element farther to the left in the perodic table or lower in the same group is usually written first. Except Cl, Br, I am written before O Prefix is used to denote the number of atoms of each element in the compound. (mono- is not used on the first element listed, however) The ending on the second element is changed to –ide o CO2: carbon o CCl4: carbon dioxide tetrachloride If element begins with a vowel and prefix ends with a or o, the final vowel is dropped from the prefix

o N2O5: dinitrogen pentoxide o CO: pentoxide carbon monoxide Nonmenclature of organic compounds     

Organic chemistry – study of compounds of carbon Hydrocarbons – compounds containing only carbon and hydrogen Alkanes – hydrocarbons containing only single bonds. Alkanes are named using prefix corresponding to the number of carbon atoms, suffix – ane Cyclic alkanes begin with prefix cyclo-

Functional groups 

Atoms other than carbon and hydrogen an/or a multiple bond in an organic compound constitute a functional group. o The –oh functional group is characteristic of alcohols. o Alcoho names end in –ol

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Isomers are compounds with the same chemical formulas but different structures 1-propanol and 2-propanol have the –OH group connected to different carbon atoms, but both have the formula C3H8O

Practice NaNO2 – sodium nitrite

HBr – hydrogen bromide/hydrobromic acid

NiCl2 – Nickel (II) Chloride

NH4Br – ammonium bromide

LiClO4 – lithium perchlorate

HgS – mercury (II) sulfide

Ca(MnO4)2 – calcium permanganate

Na2HPO4 – sodium hydrogen Phosphate

Ti(OH)4 – titanium (IV) hydroxide

KH2PO4 – potassium dihydrogen phosphate

CH3OH - methaol

CH4 – methane

1-cyclopentanol/cyclopentanol

2-butanol

cyclopropane

Determining molecular formula for compounds    

If we know the empirical formula and the molar mass of a compound, we can also know the molecular formula Molecular formula was always a whole number multiple of the empirical formula Molecular formula = empirical formula x n, where n =1,2,3... o C2H4O2=(CH2O) x 2 = CnH2nOn Can find n by calculating the ratio between the molar mass and the molecular formula o N = molar mass/empirical formula molar mass

Chemical reaction – process in which one or more substances (reactants) are converted into one or more different substances (products). Reactions required a change in the chemical bonding in every chemical reaction, bonds are made and/or broken Reactions can be represented with chemical equations. Chemical formulas of reactants, separated by plus signs, are always shown on the left side of a reaction arrow. The formulas of products, separated by plus signs are shown on the right side

Other information, including reaction conditions, solvents, and catalyst, can be indicated above or below the reaction arrow.

Sometimes a phase designated, or state symbol indicates the phase or state of matter in parentheses following a formula (solid = s, liquid = l, gas = g, aqueous = aq)

Balanced chemical equation includes coefficient before each formula indicating arrow must be the same.

General tips for balancing chemical equations o o

Start by balancing an element that appears in the fewest formulas in the equation and work toward elements that appear in more formulas Ideally, coefficients should be smallest possible whole numbers. Avoid fractional coefficients, and check for your coefficients for a common divisor.

Combustion analysis   

Another way to obtain empirical formulas for unknown compounds, especially carbon and hydrogen When unknown sample undergoes combustion in the presence of pure oxygen, all of the carbon converts to CO2 and all the hydrogen converts to H2O The amount of CO2 and H2O can be weighed; use the numerical relationships between moles to determine the amount of C and H in the original sample o Can determine the amounts of any other elemental constituents, such as O, CL or N, by subtracting the sum of the masses of C and H from the original mass of the sample...