CHM1046 Advanced Chemistry Q & A w/ Rationales 2024, Exams of Chemistry

Download CHM1046 Advanced Chemistry Q & A w/ Rationales 2024 and more Exams Chemistry in PDF only on Docsity!

CHM

Advanced Chemistry

Q & A w/ Rationales

1. Which of the following statements is true about the relationship between entropy and Gibbs free energy? a) Entropy is the measure of disorder in a system, and Gibbs free energy is the measure of the maximum amount of work that can be done by a system at constant temperature and pressure. b) Entropy is the measure of the spontaneity of a process, and Gibbs free energy is the measure of the change in enthalpy minus the change in entropy multiplied by the temperature. c) Entropy is the measure of the heat transfer in a reversible process, and Gibbs free energy is the measure of the change in entropy minus the change in enthalpy divided by the temperature. d) Entropy is the measure of the randomness of a system, and Gibbs free energy is the measure of the tendency of a system to change to a lower energy state. * Rationale: Option d) is correct because entropy is a measure of how dispersed or random the energy of a system is, and Gibbs free energy is a measure of how likely a system will undergo a spontaneous change to a more stable state. Option a) is incorrect because entropy is not directly related to work, but rather to heat transfer. Option b) is incorrect because it confuses the definitions of entropy and Gibbs free energy. Option c) is incorrect because it reverses the signs of enthalpy and entropy in the formula for Gibbs free energy.

the change in pH. d) An acid-base reaction involves the change in pH, while a redox reaction involves the change in oxidation state. Rationale: Option a) is correct because an acid-base reaction is defined as a reaction where an acid donates a proton (H+) to a base, while a redox reaction is defined as a reaction where one species loses electrons (oxidation) and another species gains electrons (reduction). Option b) is incorrect because it reverses the definitions of acid-base and redox reactions. Option c) is incorrect because an acid-base reaction does not necessarily involve a change in oxidation state, and a redox reaction does not necessarily involve a change in pH. Option d) is incorrect because it confuses the effects of acid-base and redox reactions with their definitions.

B:

1. What is the purpose of a catalyst in a chemical reaction? a) To increase the overall energy of the reactants b) To decrease the activation energy of the reaction c) To increase the concentration of the reactants d) To decrease the overall energy of the products Answer: b) To decrease the activation energy of the reaction. Rationale: Catalysts work by providing an alternative pathway with a lower activation energy, allowing the reaction to occur more easily.
2. The process of converting a compound from a liquid to a gaseous state is known as: a) Dissociation b) Condensation c) Vaporization d) Evaporation Answer: c) Vaporization. Rationale: Vaporization is the transition from liquid to gas, typically occurring when the compound is heated.
3. Which of the following reactions is an example of an acid-base reaction? a) Na + Cl₂ - > NaCl b) CH₃OH + O₂ - > CO₂ + H₂O c) HCl + NaOH - > NaCl + H₂O

ionization energy? a) Sodium (Na) b) Potassium (K) c) Calcium (Ca) d) Chlorine (Cl) Answer: d) Chlorine (Cl). Rationale: Chlorine has the highest ionization energy among these options because it requires the most energy to remove an electron from its outer shell.

7. How many sigma (σ) and pi (π) bonds are present in a double bond between two carbon atoms? a) 2 σ bonds and 1 π bond b) 1 σ bond and 1 π bond c) 1 σ bond and 2 π bonds d) 2 σ bonds and 2 π bonds Answer: d) 2 σ bonds and 2 π bonds. Rationale: In a double bond between carbon atoms, there are two sigma (σ) bonds and two pi (π) bonds formed by the overlapping of p-orbitals.
8. Which of the following is NOT a type of intermolecular force? a) Dispersion forces b) Covalent bonds c) Hydrogen bonding d) Dipole-dipole interactions

Answer: b) Covalent bonds. Rationale: Covalent bonds are intramolecular forces occurring within a molecule, while the options listed are intermolecular forces occurring between different molecules.

9. Which of the following substances exhibits metallic bonding? a) NaCl b) CO₂ c) Fe d) H₂O Answer: c) Fe. Rationale: Metallic bonding occurs in metals, such as iron (Fe), where delocalized electrons are shared among a lattice of metal atoms.
10. Which of the following is an example of an exothermic reaction? a) Combustion of gasoline b) Photosynthesis c) Dissolving salt in water d) Melting ice Answer: a) Combustion of gasoline. Rationale: Combustion reactions typically release energy in the form of heat, making them exothermic.
11. What is the purpose of a buffer solution?

Rationale: Oxygen typically has an oxidation state of - 2. In hydrogen peroxide (H₂O₂), the total charge of the molecule is zero, so the two hydrogen atoms each have an oxidation state of +1, balancing the overall charge.

14. Which of the following is an example of a redox reaction? a) AgNO₃ + NaCl - > AgCl + NaNO₃ b) H₂O → H₂ + O₂ c) CO₂ + 2H₂O → CH₃COOH + O₂ d) C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O Answer: d) C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O Rationale: In this reaction, glucose (C₆H₁₂O₆) is oxidized to form carbon dioxide (CO₂), while oxygen (O₂) is reduced to form water (H₂O).
15. Which of the following is an indicator of a spontaneous reaction? a) ΔG < 0 b) ΔG > 0 c) ΔG = 0 d) ΔH < 0 Answer: a) ΔG < 0 Rationale: ΔG represents the change in Gibbs free energy, which indicates the spontaneity of a reaction. If ΔG is negative, it means the reaction is spontaneous and can occur without the addition of external energy.

C:

Question: A student is conducting an experiment to determine the activation energy of a chemical reaction. Which of the following techniques would be most suitable for this purpose? A) NMR spectroscopy B) X-ray crystallography C) Differential scanning calorimetry D) Mass spectrometry Answer: C) Differential scanning calorimetry Rationale: Differential scanning calorimetry is specifically designed to measure the heat flow into or out of a sample as a function of temperature, making it well- suited for determining activation energy. Question: When a gas is subjected to Boyle's Law, which of the following properties remains constant? A) Temperature B) Volume C) Pressure D) Number of moles Answer: D) Number of moles Rationale: Boyle's Law states that at constant temperature, the product of pressure and volume is constant. Therefore, when pressure and volume change, the number of moles must remain constant. Question: In the context of chemical kinetics, what does the

compound. Question: Which of the following statements best describes the function of a catalyst in a chemical reaction? A) It increases the activation energy of the reaction. B) It decreases the rate of the reaction. C) It provides an alternative reaction pathway. D) It alters the stoichiometry of the reaction. Answer: C) It provides an alternative reaction pathway. Rationale: A catalyst provides an alternative reaction pathway, lowering the activation energy and facilitating the reaction without being consumed in the process. Question: In a galvanic cell, where does oxidation occur? A) Anode B) Cathode C) Salt bridge D) Electrolyte solution Answer: A) Anode Rationale: Oxidation occurs at the anode in a galvanic cell, where electrons are lost as the oxidation half-reaction takes place. Question: What is the primary function of a buffer solution? A) To resist changes in pH B) To accelerate chemical reactions C) To increase the solubility of salts D) To neutralize strong acids Answer: A) To resist changes in pH

Rationale: A buffer solution is designed to maintain a relatively constant pH even when exposed to small amounts of acids or bases. Question: Which of the following is a characteristic of an ideal gas? A) It has strong intermolecular forces. B) It occupies a negligible volume. C) It exhibits significant deviations from the ideal gas law. D) It experiences no collisions with other gas molecules. Answer: B) It occupies a negligible volume. Rationale: An ideal gas is a theoretical gas composed of a collection of randomly moving point particles that do not occupy any volume. Question: In a nuclear reaction, which of the following particles is emitted from the nucleus of an atom? A) Proton B) Neutron C) Electron D) Alpha particle Answer: D) Alpha particle Rationale: An alpha particle is a type of nuclear decay product that consists of two protons and two neutrons, emitted from the nucleus of an atom. Question: What is the term for the minimum amount of energy required to initiate a chemical reaction? A) Activation energy

frame. Question: Which of the following factors can affect the rate of a chemical reaction? A) Temperature only B) Concentration of reactants only C) Pressure only D) Temperature, concentration of reactants, and presence of a catalyst Answer: D) Temperature, concentration of reactants, and presence of a catalyst Rationale: The rate of a chemical reaction can be influenced by temperature, the concentration of reactants, and the presence of a catalyst, all of which impact the collision frequency and energy of the reacting particles. Question: What is the term for a reaction in which the heat content of the system changes? A) Isobaric reaction B) Isothermal reaction C) Adiabatic reaction D) Exothermic reaction Answer: D) Exothermic reaction Rationale: An exothermic reaction is a chemical reaction that releases energy in the form of heat, causing a decrease in the heat content of the system.