General Chemistry Exam Review, Exams of Chemistry

Download General Chemistry Exam Review and more Exams Chemistry in PDF only on Docsity! CHM 1010 General Chemistry COMPLETED EXAM 2024 1. What is the difference between a homogeneous and a heterogeneous mixture? Give an example of each. Answer: A homogeneous mixture is one that has a uniform composition throughout, such as air or salt water. A heterogeneous mixture is one that has different compositions in different regions, such as oil and water or sand and sugar. 2. What is the difference between an empirical and a molecular formula? Give an example of each. Answer: An empirical formula is the simplest ratio of the elements in a compound, such as CH for benzene. A molecular formula is the actual number of atoms of each element in a molecule of a compound, such as C6H6 for benzene. 3. What is the difference between a strong and a weak acid? Give an example of each. Answer: A strong acid is one that completely dissociates in water, releasing all its hydrogen ions, such as HCl or H2SO4. A weak acid is one that partially dissociates in water, releasing only some of its hydrogen ions, such as CH3COOH or H3PO4. 4. What is the difference between an endothermic and an exothermic reaction? Give an example of each. Answer: An endothermic reaction is one that absorbs heat from the surroundings, such as melting ice or photosynthesis. An exothermic reaction is one that releases heat to the surroundings, such as burning wood or respiration. 5. What is the difference between oxidation and reduction? Give an example of each. Answer: Oxidation is the loss of electrons or increase in oxidation number of an atom or ion, such as Mg -> Mg2+ + 2e-. Reduction is the gain of electrons or decrease in oxidation number of an atom or ion, such as Cu2+ + 2e- -> Cu. Actual Yield - Correct Answer-The amount of product ACTUALLY produced by a chemical reaction. Always equal to or less than the Theoretical Yield because a small mount of product is usually lost to other reactions or foes not form during a reaction. Percent Yield - Correct Answer-The percentage of the Theoretical Yield that was actually obtained. Expressed as the ratio of the actual yield to the theoretical yield. % Yield = (Actual amount of product formed/ Maximum [possible] amount of product) x 100% OR (Actual Yield / Theoretical Yield) x 100% Solution, Solute, Solvent - Correct Answer-Solution = Mixture of two substances Solute = What is being dissolved Solvent = What the solute is being dissolved in Aqueous Solution - Correct Answer-A solution in which water is the solvent Dilute Solution - Correct Answer-Low solute to solvent concentration (solution = less solute/more solvent) Concentrated Solution - Correct Answer-High solute to solvent concentration (solution = more solute/less solvent) Molarity (M) - Correct Answer-Mol of solute / L of solution Stock Solutions - Correct Answer-A highly concentrated form of a solution used in laboratories to make less concentrated solutions via Dilution. Dilution => M1V1 = M2V2 mol 1 = mol 2 NOTES: M1 = Molarity of initial concentrated solution V1 = Volume of initial concentrated solution M2 = Molarity of final diluted solution V2 = Volume of final diluted solution ***Number of moles of solute does not change when diluting a solution What happens if to a Dilution solution if the volume is doubled? - Correct Answer-The Molarity would be halved because the Molarity of the Dilution solution (M2) is inversely proportional to the volume of the Dilution solution (V2) Molarity (Conversion Factor) - Correct Answer-The equation for Molarity can also be used as a Conversion Factor (Fraction) Mol of solute / 1 L of solution Families of Organic Compounds - Correct Answer-1.) Alcohols 2.) Ethers 3.) Aldehydes 4.) Ketones 5.) Carboxylic Acids 6.) Esters 7.) Amines 8.) Amides Alcohols (Name ending/Example of compound/Use)? - Correct Answer-***Look at Powerpoint for the General formula/Example chemical structure 1.) Name ending = -ol 2.) Example of compound = Ethanol 3.) Use = Alcohol in fermented beverages Ethers (Name ending/Example of compound/Use)? - Correct Answer-***Look at Powerpoint for the General formula/Example chemical structure 1.) Name ending = ether 2.) Example of compound = Diethyl ether 3.) Use = Anesthetic; laboratory solvent Aldehydes (Name ending/Example of compound/Use)? - Correct Answer-***Look at Powerpoint for the General formula/Example chemical structure 1.) Name ending = -al 2.) Example of compound = Propanol 3.) Use = Perfumes; flavors Ketones (Name ending/Example of compound/Use)? - Correct Answer-***Look at Powerpoint for the General formula/Example chemical structure 1.) Name ending = -one 2.) Example of compound = Acetone 3.) Use = Fingernail polish remover Carboxylic acids (Name ending/Example of compound/Use)? - Correct Answer-***Look at Powerpoint for the General formula/Example chemical structure 1.) Name ending = acid 2.) Example of compound = Acetic acid 3.) Use = Vinegar Esters (Name ending/Example of compound/Use)? - Correct Answer-***Look at Powerpoint for the General formula/Example chemical structure 1.) Name ending = -ate 2.) Example of compound = Methyl acetate 3.) Use = Laboratory solvent Amines (Name ending/Example of compound/Use)? - Correct Answer-***Look at Powerpoint for the General formula/Example chemical structure 1.) Name ending = amine 2.) Example of compound = Ethyl amine 3.) Occurrence = Smell of rotten fish Amides (Name ending/Example of compound/Use)? - Correct Answer-**Look at Powerpoint for the General formula/Example chemical structure 1.) Name ending = -amide 2.) Example of compound = Acetamide 3.) Use = Industrial solvent What do Stoichiometric Equivalents look like in mathematical equations? - Correct Answer-Conversion Factors (fractions) Example: 2H2 + O2 --> 2H2O (2 mol H2 / 1 mol O2) OR (1 mol H2 / 2 mol H2) (2 mol H2 / 2 mol H2O) OR (2 mol H2O / 2 mol H2) Examples: 1.) Putrescine -- NH2 (CH2)4 NH2 2.) Cadaverine --NH2 (CH2)5 NH2 How many moles are present in a Diluted Solution? (Stock Solution vs. Dilution Solutions) - Correct Answer-Nothing happens--the number of moles stays constant throughout. If you are looking at a chemical diagram, what do you think happens to the amount of solute if the volume is doubled? - Correct Answer-Just as stated with the Dilution equation (if you haven't already gotten around to looking at it), the molarity of the initial (Stock) solution (M1) is inversely proportional to the volume of the initial solution (V1) and similarly for the final (Diluted) Solution What happens when a solid is submerged into a solvent? - Correct Answer-The solute- solute (intramolecular) interactions fight with the solute-solvent (intermolecular) interactions Hydration Shells appear... Example: NaCl (Table Salt) [Na +] encompassed by O atoms from H2O [Cl -] encompassed by H atoms from H2O Electrolytes - Correct Answer-A substance that dissolves in water to form solutions that conduct electricity. Pretty much... IONS Examples: Na+, Cl-, Ca 2+, O 2- Strong Electrolytes - Correct Answer-A substance that completely dissociates into ions when dissolved in water. Example: Ionic compounds (ex: NaCl) Non-electrolytes - Correct Answer-A compound that does not dissociate into ions when dissolved in solution. Therefore, the resulting solution does not conduct electricity. Examples: C6H12O6 (sugar) Weak acids (revisited but in Electrolyte/Non-electrolyte solutions) - Correct Answer-Acids that do not completely ionize (dissolve) in solution. Weak Electrolytes - Correct Answer-A substance that does not completely lionize (dissociate) in water and only weakly conducts electricity in solution. --Weak acids, among others... Weak electrolyte solutions result, conducting electricity very weakly. Soluble - Correct Answer-Used to describe a substance that dissolves in water Example: AgNO3 (aq) Insoluble - Correct Answer-Used to describe a substance that does not dissolve in water Example: AgCl (s) Solubility Rules (Read diagram for extensive info) - Correct Answer- General Formulas of Alcohols - Correct Answer- General Formulas of Ethers - Correct Answer- General Formulas of Aldehydes - Correct Answer- General Formulas of Ketones - Correct Answer- General Formulas of Carboxylic acids - Correct Answer- General Formulas of Esters - Correct Answer- General Formulas of Amines - Correct Answer-RNH2 General Formulas of Amides - Correct Answer-RCONH2 Solubility Rules (see diagram) - Correct Answer- Precipitation Reactions - Correct Answer-A reaction in which a solid, insoluble product forms when 2 solutions are mixed. Example: 2KI(aq) + pb(NO3)2(aq) --> PbI2(s) + 2KNO3(aq) --> PbI2(s) = Precipitate formed from reaction NOTE: - Even though the reactants are generally aqueous solutions, 1 product will still be in the solid state depending on its solubility in water. Precipitate - Correct Answer-A solid, insoluble ionic compound that forms in, and separates from, a solution. The solid form depends on its solubility in water, otherwise we cannot assume a product to be in the solid form and thereby a Precipitate. Molecular Equation (*see diagram) - Correct Answer-An equation showing the complete neutral formula for each compound in a reaction. Example: (*see diagram) Complete Ionic Equation (*see diagram) - Correct Answer-An equation that lists individually all of the ions present as either reactants or products in a chemical reaction. Example: (*see diagram) NOTE: - Only the product that has underwent a change in its physical state from the "aqueous" state of a solution stays (non-ionized) - Every other reactant/product is shown to be ionized in the Complete Ionic Equation - Do not separate (ionize) weak electrolytes in a Complete Ionic Equation. Spectator Ions - Correct Answer-Ions in a Complete Ionic Equation that do not participate in the reaction and therefore remain in solution. Ions that are not part of the reaction that undergoes a change in composition (or transformation of molecules from their original state as Reactants) NOTE: - Spectator Ions are not included in the Net Ionic Equation because they stay in the solution (completely ionized) Net Ionic Equations (*see diagram) - Correct Answer-An equation that shows only the species that actually change during the reaction (physical state from an "aqueous" solution to a "solid" state or "liquid" state or "gaseous" state) Example: (*see diagram) NOTE: - The Equivalence Point is usually signaled by an Indicator (a dye whose color depends on the acidity or basicity of the solution). Indicator (Equivalence Point in Acid-Base Titration) - Correct Answer-A dye whose color depends on the acidity or basicity of the solution. Used to determine the Equivalence Point in Acid-Base Titration. Gas-Evolution Reactions - Correct Answer-A reaction in which 2 aqueous solutions mix together to form a gaseous product that bubbles out of solution. Example: H2SO4(aq) + Li2S(aq)-->H2S(g) + Li2SO4(aq) How are Gas-Evolution Reactions and Acid-base Reactions similar? - Correct Answer- They both produce water as a product. What kind of reaction can Gas-Evolution Reactions be thought of as? - Correct Answer- Acid-Base Reactions because Gas-Evolution Reactions produce water as well as gaseous products. What is distinct about Gas-Evolution Reactions? - Correct Answer-They have an intermediate product, such as a weak base (e.g. H2CO3), that dissociates into H2O and CO2. How can you tell if one strong electrolyte is "stronger" than another strong electrolyte? - Correct Answer-Depending on the number of dissociated ions, the "stronger" strong electrolyte is the one with more ions. Oxidation-Reduction Reactions (Redox Reactions) - Correct Answer-Reactions in which electrons are transferred from one reaction to another and the oxidation states of certain atoms are charged. Oxidation - Correct Answer-1.) The loss of electrons 2.) The increase in oxidation state Reduction - Correct Answer-1.) The gain of electrons 2.) The decrease in oxidation state Oxidation State (or Oxidation Number)? - Correct Answer-A positive or negative whole number that represents the "charge" an atom in a compound would have if all shared electrons were assigned to the atom with a greater attraction for these electrons. Rules for Assigning Oxidation States? - Correct Answer-1.) The oxidation state of an atom in a free element is 0. 2.) The oxidation state of a monoatomic ion is equal to its charge. 3.) The sum of the oxidation states of all atoms in: - A neutral molecule or formula unit is 0. - An ion is equal to the charge of the ion. 4.) In their compounds, metals have positive oxidation states. - A Group 1A metals always have an oxidation state of +1. - A Group 2A metals always have an oxidation state of +2. 5.) In their compounds, nonmetals are assigned oxidation states according to the table shown here. Entries Thermochemistry? - Correct Answer-The study of the relationship between chemistry and energy. Energy? - Correct Answer-The capacity to do work. Expressed in joules (J) Work? - Correct Answer-The result of a force acting through a distance. Heat - Correct Answer-The flow of energy caused by a temperature difference. Kinetic Energy - Correct Answer-The energy associated with an object's motion Expressed as KE = 1/2 x mv^2 Thermal Energy - Correct Answer-A type of kinetic energy associated with the temperature of an object, arising from the motion of individual atoms or molecules in the object. Potential Energy - Correct Answer-The energy associated with the position or composition of an object. Expressed as PE = mgh Chemical Energy - Correct Answer-The energy associated with the relative positions of electrons and nuclei in atoms and molecules. The Law of Conservation of Energy? - Correct Answer-A law stating that energy can neither be created nor destroyed, only converted from one form to another. System? - Correct Answer-In Thermodynamics specifically, the portion of the universe that is singled out for investigation Universe (Formula)? - Correct Answer-E(universe) = E(system) + E(surroundings) 'E' = energy Surroundings? - Correct Answer-Everything in the universe that exists outside the system under investigation. Joule (J) - Correct Answer-The amount of energy needed to exert the force of 1 Newton over a distance of 1 meter. Units: 1 kg x m^2 / s^2 Calorie (cal)? - Correct Answer-A unit of energy defined as the amount of energy required to raise 1 g of water by 1 C. Equal to 4,184 J. Kilowatt-hour (kWh)? - Correct Answer-An energy unit used primarily to express large amounts of energy produced by the flow of electricity. Equal to 3.60 x 10^6 J Thermal Equilibrium? - Correct Answer-The point at which there is no additional net transfer of heat between a system and its surroundings. Heat Capacity (C)? - Correct Answer-The quantity of heat required to change a system's temperature by 1 C. How to calculate Heat (J) in regards to temperature change (deltaT), heat capacity(J/g x C), and mass(g)? - Correct Answer-q = m x C x deltaT q = heat m = mass (g) C = heat capacity deltaT = temperature change in celsius What is the equation for thermal energy transfer? - Correct Answer-Qsys = -Qsurr NOTE: - This means the the energy lost by the surroundings is equal to the energy gained by the system. - Use the equation for heat (q = m x C x deltaT) 3.) Vibrational motion Translational Motion? (diagram) Rotational Motion? (diagram) Vibrational Motion? (diagram) - Correct Answer-Refer to ch.6 powerpoint slide #9 What kinds of interactions are associated with Potential Energy? - Correct Answer-1.) Intramolecular interactions 2.)Intermolecular interactions Energy Conversion Factors - Correct Answer-1 calorie (cal) = 4.184 joules (J) 1 Calorie (Cal) = 1000 cal = 1 kcal = 4184 J 1 kilowatt-hour (kWh) = 3.60 x 10^6 J 1 L x atm = 101.3 J Formulas for Internal Energy (deltaE) - Correct Answer-deltaE = q + w NOTE: -- Remember to find the "sign" of the value for work (w). -- Expansion of a gas = Negative (-) work (Work being done BY the system) -- Compression of a gas = positive (+) work (Work being done ON the system) -- Combustion = negative (-) deltaE (energy is released/lost by the system) -- Endothermic Reactions = Positive (+) deltaE -- Exothermic Reactions = Negative (-) deltaE Formula for Work (w) - Correct Answer-Pressure-Volume work => w = -P(external) x [change in volume (deltaV)] Formulas for Heat (q) - Correct Answer-q = m x C x deltaT => units are "KJ / mol" q = C x deltaT = units are "Joules (J)" m = mass (g) C = specific heat capacity/molar heat capacity deltaT = change in temperature (state function=> "final T (*C) - initial T (*C)") NOTE: -- C is expressed in J/g*C or J/g*K -- J/g*C = J/g*K How does Molar Heat Capacity (units-wise) differ from Specific Heat Capacity (units- wise)? - Correct Answer-Molar Heat Capacity is expressed in KJ / mol where the heat (q) [ C x deltaT ] is divided by the mol of reactant. What is the Bomb Calorimeter used to measure exactly? - Correct Answer-delta E (internal energy) What is the Coffee Cup Calorimeter used to measure exactly? - Correct Answer-delta H (enthalpy) Summarize the equivalence of delta H and delta E in relation to the q(rxn) - Correct Answer-=> - delta E = q(rxn) => - delta H = q(rxn)