学习日记（foundation-chemistry)
chapter 4：Chemical Composition
-所有物质都是化学的，或者物理组合成物质。
- Experiencing Atoms
-所有element是从不同的atom做出来的
-所有的atom有eletron（-ve），proton（+ve）和neutron（neutral）
-proton和neutron被packed在小小的中心叫nucleus，然后它的外围是有electron聚集的
-所有的atoms被认为是球体
- Sizes of Atoms
。被认为是球体，然后也被叫成atomic radius
。 atomic volume增加当atomic number of atom increase
-Mass of atom
。Atomic mass unit (amu)（1 amu = 1.6605 x 10^-24）
*大部分发现的element是在大自然的作为mixture of isotopes
*所有的isotopes在一个atom是存在specific ratio 被称为abundance
*Atomic mass of an atom Y= ΣX1 M isotopeY1 + X2 M isotopeY2+….
X1, X2 are abundance of isotope Y
M1, M2 are relative mass unit of isotope Y
。Molar mass of atom（mass of 1 mol of atom (g/mol or gmol-1)
。Formula mass （mass of 1 mol of molecule/formula (g/mol)）
- Counting Atoms by Moles
-The number of atoms use is 6.022 x 10^23(Avogadro’s number.)
- mole concept
- Relationship Between Moles and Mass
-一个element的molar mass 是以g为单位，也是可以用amu来做单位
-越轻的atom，越少mole weigh
-越轻的atom，越多atom当它在1g的时候
- Relationships of Mole and Volume
-气体的体积会被温度和压力影响（Gas Law）
-体积与气体类型无关
- Percent Composition
。By mass.
-Can be determined from:
。The formula of the compound.
。The experimental mass analysis of the compound.
-The percentages may not always total to 100%
due to rounding.
- Quantities in Chemical Reactions
。Law of Conservation of Mass.
。Balancing equations by balancing atoms.
-stoichiometry是为了研究numerical relationship between chemical quantities in a chemical
reaction数值关系化学含量之间反应
- Mole-to-Mole Conversions
-在反应和平衡的化学方程允许我们从任何化学物质在反应量到任何其他。
- Theoretical and Actual Yield
the amount of product each of the reactants could make.
-The theoretical yield will always be the least possible amount of product.
。The theoretical yield will always come from the limiting reactant.
-Because of both controllable and uncontrollable factors, the actual yield of product will always be
less than the theoretical yield.
- Solutions
。似乎是一种物质，虽然真的包含多个材料。
-Heterogeneous mixtures
-Heterogeneous mixtures
。似乎有两个或两种以上的物质，你可以看到各个组件
-solute 是会溶解的东西
。看上去是“消失”的
。“Takes on the state” of the solvent.
-Solvent收溶解在里面的solute
。它是不会改变它的state的
-当2个solute和solvent在同一个state，solvent的component 会呈现更高的percentage
-溶剂为水的solution叫aqueous solutions.
- Common Types of Solution
- Solubility
-当一种物质（solute）溶解在另一种物质中时（solvent）我们可以称之为soluble或者miscible
。盐可以被溶于水
。气体用于可以溶于彼此
-当其中一个东西不能溶于另一个我们可称之为insoluble
。油不能溶于水
-最大solute量溶解在一定量的solvent中可称之为solubility
-solubility可以被2个因素影响：nature’s tendency towards mixing
and the types of intermolecular attractive forces.自然混合的倾向和分子间吸引力的种类。
- Will It Dissolve?
-一个solvent将会被溶解当它的构造跟另一个solvent相似
-物质会有相似的intermolecular forces来dissolve each other
- Intermolecular Forces in Solution
。水里面的Ionic compounds
。Water molecules 聚集在那些ions 的hydration shells.
-Hydrogen bonding
。Especially important in aqueous solution
。Hydrogen atom in a polar bond (H-F, H-O andH-N bond)
-Dipole-dipole forces
。Account for the solubility of polar molecules
-Ion-induced dipole forces
。依靠在 the polarizability of the components
。Ion’s charge distorts扭曲 the electron cloud of a non polar molecule
-Dipole-induced dipole forces
。Based on polarizability
。比 ion-induced dipole force弱. Dipole charge 较小
。Polar charge distorts扭曲 the electron cloud of a non polar molecule
-Dispersion forces
。Principle type intermolecular forces in solutions of nonpolar substance
- Classifying Solvents
- Will It Dissolve in Water?
。Many ionic compounds dissolve in water.
-Polar molecules are attracted to polar solvents.
。Table sugar, ethyl alcohol, and glucose all dissolve well in water.
*Have either multiple OH groups or little CH.
-Nonpolar molecules are attracted to nonpolar solvents.
。β-carotene (C40H56) is not water soluble; it dissolves in fatty(nonpolar) tissues.
-很多 molecules 有both polar and nonpolar structures—它们是否会溶于水取决于分子中polar和nonpolar结构特征的种类、数量和位置.- Solvated Ions
- Descriptions of Solubility
。溶液的最大溶质量，在该温度下溶解在溶剂中。solutions have the maximum amount of solute that will dissolve in that solvent at that temperature.
-Unsaturated
。溶液可以溶解更多的溶质。solutions can dissolve more solute.
-Supersaturated
。溶液持有更多的溶质比他们应该能够在温度。solutions are holding more solute than they should be able to at that temperature.
*unstable
- Solution Concentrations
-要描述solution，您需要描述component及relative amounts.
-Dilute solutions=有少量的solute在每一个solution。
-Dilute solutions=有少量的solute在每一个solution。
-Concentrated solutions=有大量的solute在每一个solution。
-描述solution的更精确方法是量化给amount of solute
in a given amount of solution.
- Unit of Concentration
-% w/v - ppb = μg/L, μg/kg
-% v/v
-Mass %
-Mol fraction
-Molarity (M)
-Molality (m)
-Normality (N)
- Parts of Solute by Parts of Solution
- Mole Fraction
- Using Concentrations as Conversion Factors
-Concentrations 显示2个solute和solvent之间的关系
-The concentration 可以用来 convert the amount of solute 进the amount of solution or vice versa.
- Concentration
- Preparing a Solution
-算所需要的solute的mass
。Start with amount of solution.
。Use concentration as a conversion factor.
。“Dissolve the grams of solute in enough solvent to total the total amount of solution.”
- Solution Concentration：Molarity
-Moles of solute per 1 liter of solution.
-用来描述多少个molecules of solute在每一liter of solution
- Using Concentrations as Conversion Factors
。0.12 M sugar (aq) means 0.12 mol sugar ≡ 1.0 L solution.
-The concentration 可以用来 convert the mole of solute 进the amount of solution or vice versa.
-通常测量 the amount of solute 是grams为单位,我们需要 convert 在 grams 和 moles之间
- Molarity and Dissociation
-通过了解formula of the compound 和 the molarity of the solution, 它是确保 the molarity of the dissociated ions. 简单multiply the salt concentration 通过 the number of ions.
- Dilution
-The amount of solute 保持一样, 但是 the concentration 减少.
-Dilution Formula:
Concstart solnx Volstart soln = Concfinal solnx Volfinal sol
-Concentrations and volumes 可以是任何units as long as 它们是consistent.
M1V1 = M2V2
- Solution Stoichiometry
2 H2(g) + O2(g) → 2 H2O(l) - 2 moles of H2 used, 1
mole of O2 needed and 2 moles H2O produced.
-Since molarity is the relationship between moles of solute and liters of solution, the moles of a material in a reaction in solution can be measured from its molarity and volume.
- Titration
-Titration is a technique that uses reaction stoichiometry to determine the concentration of
an unknown solution.
-Titrant (unknown solution) is added from a buret.
-Indicators are chemicals that are added to help determine when a reaction is complete.
-The endpoint of the titration occurs when the reaction is complete.
- Acid–Base Titration
-As the base is added to the acid, the H+ reacts with the OH– to
form water. But there is still excess acid present, so the color does not change.
-At the titration’s endpoint, just enough base has been added to
neutralize all the acid. At this point, the indicator changes color: [H+] = [OH–]
- Solution Concentration:Normality (N)
-No. of equivalents = Normality x VL = (eq/L) x L
-No. of milliequivalents = Normality x VL= (meq)/L) x mL
-No.of equivalents = wt(g)/equivalents weight(g/eq)
-No.of milliequivalents = wt (mg)/equivalent weight(mg/meq)
-Equivalents can be defined in several ways.
。The number of moles of H+ or OH- ions replaced in a chemical reaction.
。The number of replaceable H+ or OH- ions in a compound.
。The number of moles of electrons transferred in a chemical reaction (redox).
*Equivalent weight (EW) = Molecular weight(MW) / Valency (Z)
-Normality is related to molarity:
Normality (N) = n x M
-Normality is useful in titrations calculations
NaVa = NbVb
-Normality is used as a measure :
1. In acid-base chemistry, normality is used to express the concentration of ions (H3O+) or ions
(OH−) in a solution. Each solute can produce one or more equivalents of reactive species when dissolved.
2. In redox reactions, the equivalence factor describes the number of electrons that an oxidizing or reducing agent can accept or donate.
3. In precipitation reactions, the equivalence factor measures the number of ions which will precipitate in a given reaction.
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