\h1{Chemical Formulas} \layout[cols=3] { \note{ \h2{Molecular Formula} \ul{ \li{Shows actual number of atoms.} \li{Used for covalently bonded atoms.} } } \note{ \h2{Empirical Formula} \ul{ \li{simplest whole-integer ratio of atoms in a compound.} \li{Used for ionic compounds -crystals that can form thousands of bonds. Such as \{\mathrm{Na}_{1000}\mathrm{Cl}_{1000}}. The Empirical Formula simplified this into just \{\mathrm{Na}\mathrm{Cl}}.} } } \note{ \h2{Structural formula} \ul{ \li{Graphical diagrams.} } } } \h1{Compounds} \layout[cols=2] { \note{ \h2{Molecular (Covalent)} \equation{ \text{nonmetal} + \text{non-metal} &\implies \text{molecular compound} } } \note{ \h2{Ionic} \equation{ \text{metal} + \text{non-metal} &\implies \text{ionic compound} } } } \h1{Terminology} \layout[cols=3] { \note{ \h2{Solutions} \ul{ \li{Solutions have previously been defined as \u{homogeneous mixtures}.} \li{The relative amount of a given solution component is known as its \u{concentration}.} \li{The \b{solvent} is some \{C_x} that is \u{significantly greater} than all other \{C_{xs}} in the given solution.} \li{A \b{solute} is a component of a solution that is typically present at a \u{much lower concentration} than the solvent. \note[inline]{Solute concentrations are often described with qualitative terms such as \b{dilute} (of relatively low concentration) and \b{concentrated} (of relatively high concentration).} } \li{This component is called the \b{solvent} and may be viewed as the \u{medium} in which the other components are \u{dispersed or dissolved}.} \li{A \b{solution} in which \u{water is the solvent} is called an \u{\b{aqueous solution}}.} } } \note{ \h2{Dilution of Solutions} \ul{ \li{\b{Dilution} is the process whereby the concentration of a solution is lessened by the \u{addition of solvent}.} \li{\b{Dilution} is also a common means of preparing solutions of a desired concentration. \note[inline]{By adding solvent to a measured portion of a more concentrated stock solution, a solution of lesser concentration may be prepared.} } \li{A simple mathematical relationship can be used to relate the volumes and concentrations of a solution before and after the dilution process.} } According to the definition of molarity, the molar amount of solute in a solution (n) is equal to the product of the solution’s molarity (M) and its volume in liters (L): \equation{ n &= ML } the dilution equation is often written in the more general form: \equation{ C_1 V_1 &= C_2 V_2 } where \{C} and \{V} are concentration and volume, respectively. \h3{Determining the Concentration of a Diluted Solution} \h3{Volume of a Diluted Solution} \h3{Volume of a Concentrated Solution Needed for Dilution} } \note{ \h2{Other Units for Solution Concentrations} \h3{Mass Percentage} \h4{Calculation of Percent by Mass} \h4{Calculations using Mass Percentage} \h4{Calculations using Volume Percentage} \h3{Mass-Volume Percentage} \ul{ \li{A mass-volume percent is a ratio of a solute’s mass to the solution’s volume expressed as a percentage.} } \h3{Parts per Million and Parts per Billion} \ul{ \li{Very low solute concentrations are often expressed using appropriately small units such as \b{parts per million} (ppm) or \b{parts per billion} (ppb).} \li{The \b{ppm} and \b{ppb} units defined with respect to \u{numbers of atoms and molecules}.} \li{Both \b{ppm} and \b{ppb} are convenient units for reporting the concentrations of pollutants and other trace contaminants in water.} } \equation{ \mathrm{ppm} &\equiv \frac{\text{mass solute}}{\text{mass solution}} \times 10^6 ppm \\ \mathrm{ppb} &\equiv \frac{\text{mass solute}}{\text{mass solution}} \times 10^9 ppb \\ } } } \h1{Units & Values} \layout[cols=3] { \note{ \h2{Atomic Mass Unit (amu) } \ul{ \li{Equivalent to Dalton (Da) and Unified Atomic Mass Unit (u).} } \equation{ 1\;\mathrm{amu} &= \frac{1}{12}\;\text{mass of carbon-12}\\ &\approx 1.6605 \times 10^{-24}\mathrm{g} } } \note{ \h2{Fundamental Unit Of Charge (e)} } \note{ \h2{Formula Mass} \equation{ \small{\text{Let}}\;\;&\\ A &= \text{“atoms in a given substance”}\\ A_{\mathrm{avg}} &= \text{“avg. mass of each atom in $A$”}\\ \small{\text{Therefore}}\;\;&\\ \text{“Formula Mass”} &= \text{“sum of all values in $A_{\mathrm{avg}}$”} = \text{“Molecular Mass”} } } \note{ \h2{The Mole} \ul{ \li{An Actually Good Explanation of Moles (YouTube) -since we can't just count how many atoms we have for a given sample, we instead use e.g. grams to measure how many atoms we have.\note[inline]{“Person 1: how much oxygen do we have there? Person 2: well you how the atomic mass of oxygen, so that, but in grams.” Moles are means of saying just such.}} } \hr \equation{ 1\;\mathrm{mole} &\approx 6.022 \times 10^{23}\\ &\approx 6.02 \times 10^{23}\\ &\approx \small{\text{“Avogadro’s number”}} } \hr Note that \equation{ 1\;\mathrm{mole} & \implies \text{“amount” unit}\\ } Therefore given any two elements \{E_1} and \{E_2} \equation{ \text{$1$ mole of $E_1$} &= \text{$1$ mole of $E_2$} } } \note{ \h2{Molar Mass} \ul{ \li{The molar mass of an element (or compound) is the mass in grams of \{1} mole of that substance.} \li{This property is expressed in units of grams per mole, \{\frac{\mathrm{g}}{\mathrm{mol}}}} \li{The mass of \u{one mole} of atoms is called the \b{molar mass}.} \li{The molar mass of an element is grams is numerically equal to the element's atomic mass (amu). e.g. 1\;\mathrm{mole}\;\text{of carbon} &= 12.011\;\mathrm{grams}\\1\;\mathrm{atom}\;\text{of carbon} &= 12.011\equation{\mathrm{amu}}} \li{\{1\;\mathrm{mole}\;\text{of carbon} = 12.011\;\mathrm{grams}}; while the weight (in amu) of \{1\;\text{carbon} = 12.011\;\mathrm{amu}}. Technically, the mass of \{1\;\mathrm{mole}} of a given substance should be denoted as \{\frac{\mathrm{g}}{\mathrm{amu}}}.} } \h3{Notes} \equation{ \text{“molar mass of a compound $C_x$ in grams”} &= \text{“formula mass of $C_x$ in amu”}\\ \text{atomic mass} &= \text{molar mass} } \table{ \tr{ \td{Element} \td{Average Atomic Mass (amu)} \td{Molar Mass (g/mol)} \td{Atoms/Mole} } \tr{ \td{C} \td{12.01} \td{12.01} \td{\{6.022 \times 10^23}} } } } \note{ \h2{Percent Composition} \ul{ \li{Works for \b{Molecular} and \b{Empirical Formulas}.} \li{Can be used for \u{determining an \b{Empirical Formula} from \b{Percent Composition}}.} } Given some compound \{C_x} \equation{ \text{“Percent Composition”} &\equiv \text{“percentage by mass of each element in $C_x$”} } Therefore given some \{E_x \in C_x} \equation{ \% E_x &\equiv \frac{\text{mass of $E_x$}}{\text{total mass of $C_x$}} \times 100\% } Note that \{E_x} may itself be a group of atoms in the case of Molecular and Empirical Formulas. \h3{Determining Empirical Formula from Percent Composition} \h3{Derivation of Molecular Formulas} \ul{ \li{Molecular formulas are derived by comparing the compound’s molecular or molar mass to its \u{empirical formula mass}. \note[inline]{As the name suggests, an empirical formula mass is the sum of the average atomic masses of all the atoms represented in an empirical formula.} } } } \note{ \h2{Molarity (M)} \ul{ \li{Molarity is defined as the \u{number of moles of solute} in exactly \u{1 liter of the solution}.} } \equation{ \mathrm{M} &\equiv \frac{\text{mol solute}}{1\; L\;\mathrm{solution}} } \h3{Tips} Given some element \{E}: \equation{ E_m &= \text{amount of $E$ in moles}\\ E_g &= \text{amount of $E$ in grams}\\ E_{\text{amu}} &= \text{Atomic weight of $E$}\\ \text{Therefore}&\\ E_g &= E_m \times E_{\text{amu}}\\ \text{Or alternatively}&\\ \text{“Grams”} &= \text{“Moles”} \times \text{“Atomic weight”} } \h3{Determining the Volume of Solution Containing a Given Mass of Solute} } }