Chem 112 Exam With Detailed Correct Verified Answers

Which of the following molecular compounds would be highly soluble in hexane, C6H14? - correct answers C6H6 Consider the three statements and pick the best answer. I. An increase in disorder favors dissolution. II. Most spontaneous processes are exothermic. III. At constant temperature, when more solid is added to a supersaturated solution, the added solid dissolves. - correct answers 1 and 2 are true, 3 is false For solubility the higher the temperature the: - correct answers less solubile Which colligative property of solutions listed below is correctly stated? I. The freezing point of a solution decreases as more solute is added. II. The boiling point of a solution increases as more solute is added. III. The vapor pressure of a volatile liquid above its solution decreases as more solute is added. - correct answers all three The equilibrium constant for the reaction below is 1.7 x 10^17 at 25 C. H2 (g) + Br2 (g) ⇌ 2 HBr (g) Kc(25 C) = 1.7 x 10^17 What can be stated about the relative equilibrium distribution for this mixture? - correct answers The mixture contains predominantly HBr at equilibrium. If Q Keq - correct answers ratio of product is smaller, reaction will move in forward direction to reach equilibrium If Q Keq - correct answers ratio of products is larger, reaction will move in reverse direction to reach equilibrium If Q = Keq - correct answers system is at equilibrium An endothermic reaction CaCO3 (s) ⇌ CaO (s) + CO2 (g) at equilibrium is suddenly cooled to a lower temperature and allowed to re-establish equilibrium at the new temperature. Which of these statements correctly describes the new equilibrium? - correct answers The equilibrium constant decreases Select all of the following which represent a basic solution. I. A solution with a hydroxide ion concentration of 1.8 ⨉ 10-6 M II. A solution with a pOH of 4.74 III. A solution with a hydronium ion concentration of 2.6 ⨉ 10-4 M - correct answers 1 and 3 only Consider the following statements. Choose all that are TRUE. I. The concentrations of H3O+ and OH in pure water at 25 ºC are both 1.0 ⨉ 10-7 M II. HSbF6 is the conjugate acid of SbF6- III. Bases act as proton donors in an acid-base reaction a. I only b. I and II only c. I and III only d. II and III only e. All of these are true - correct answers B Consider the weak acids below and their corresponding Ka values. Rank the acids from weakest to strongest. HCN (Ka = 6.2 ⨉ 10-6 ) CH3COOH (Ka = 1.8 ⨉ 10-5 ) HF (Ka = 6.6 ⨉ 10-4 ) - correct answers (weakest) HCN CH3COOH HF (strongest) When mixed in equal molar amounts, which of the following pairs of substances would create a buffer? - correct answers HCN and NaCN In the titration of HCN with KOH, which species (besides water) is/are present at the equivalence point? - correct answers KCN only For a reaction with the rate law below: Rate = k[A] - correct answers a plot of ln [A] vs. time gives a straight line Which of the following will decrease the activation energy, Ea, of a reaction? - correct answers adding a catalyst If q of the system is negative: - correct answers the surroundings are heated by the system Select all of the following reactions that would be expected to provide a negative change in entropy, delta S 0. I. 2 K (s) + F2 (g) → 2 KF (s) II. 2 NO2 (g) → N2O4 (g) III. NaClO3 (s) → Na+ (aq) + ClO3 1− (aq) - correct answers 1 and 2 only Under standard conditions, a positive value of delta G for a reaction indicates that: - correct answers the reaction is non-spontaneous in the forward direction For a given chemical reaction, the value of deltaH is negative and the value of delta S is positive. The value of delta G for this reaction indicates that the reaction is: - correct answers spontaneous at all temperatures he equilibrium constant for the reaction below is 3.2 × 10−34 at 25 °C. 2 HCl (g) ⇌ H2 (g) + Cl2 (g) Keq(25 °C) = 3.2 × 10−34 Which of the following statements is true about the system at equilibrium? - correct answers The mixture contains predominantly HCl. The following are factors that influence the rate of the reaction: N2 (g) + 3H2 (g) → 2 NH3 (g). Which are stated correctly? I. The rate increases when the concentration of reactant decreases. II. The rate increases when a catalyst is added. III. The rate increases when the temperature increases. - correct answers 2 and 3 only Ethylene glycol is mixed with water and added to an automobile's radiator. Which of the following occurs? I. The freezing temperature of the mixture rises. II. The vapor pressure inside the radiator increases. III. The boiling temperature of the mixture rises. - correct answers 3 only . In which solvent would the solubility of sodium nitrate, NaNO3, be greatest? - correct answers H2O The reaction 2 NO (g) + 2 CO (g) ⇌ N2 (g) + 2 CO2 (g) was allowed to reach equilibrium. Additional CO gas was then injected into the reaction chamber and equilibrium was restored. Choose the correct statement below. - correct answers A new equilibrium is obtained such that [NO] decreases. Which of the following is associated with a redox reaction that would proceed spontaneously towards the product side of the equation without having any outside work supplied to the system? I. ΔG 0 II. Ecell 0 III. Q K - correct answers all 3 For a given chemical reaction, the value of ∆H is positive and the value of ∆S is positive. The value of ∆G for this reaction indicates that the reaction is: - correct answers spontaneous only at high temperatures