TPR General Chemistry

TEST 1 6. Based on information given in the passage, the reactivity series for nonmetals is best predicted by: A) electron affinity. B) electronegativity. C) reduction potential. D) oxidation state. If the gas is more reactive than the nonmetal in the ionic compound, it will displace that nonmetal and create a new salt. F2(aq) + 2 KI(aq) 2 KF(aq) + I2(aq) F2 > Cl2 > O2 > Br2 > I2 electron affinities for fluorine and chlorine are -328 kJ/mol and -349 kJ/mol

Analysis Chose A because thought because if eletron is more likely to gain an electron then it has higher electron affinity. According to the F2(aq) + 2 KI(aq) 2 KF(aq) + I2(aq). F becomes reduced, which means it has higher electron affinity and reduction potential. Since the passage was about affinity then choose A. TEST: Reduction potential, electron affinity LEARN: list all the trends The passage states that the electron affinity for fluorine is less negative than that of chlorine, yet the reactivity of fluorine is greater than that of chlorine. C

TEST 2 19. If the n = 4 to n = 3 transition of an atom emits yellow light, which of the following transitions in this same atom could emit red light? A) The n = 4 to n = 2 transition B)The n = 3 to n = 2 transition C)The n = 5 to n = 4 transition D)The n = 1 to n = 2 transition

Concept - spectrum and orbital energy ROYGBV. R is less energy than Y light. Then the emission should be less energy. If the oribitals are higher then there is more energy. Chose B because 3 to 2 emits less energy than 4-3. TEST: spectrum and orbital LEARN: energy levels↓ with ↑ distance from the nucleus C

TEST 1 Bio section 58. Ten mL of a 1 M NaOH solution is added to equal volumes of two saturated solutions. One solution contains an excess of Zn(OH)2(s) and the other an excess of Fe(OH)2(s). Why does more Zn(OH)2 dissolve in the first flask, but more Fe(OH)2 precipitate in the second flask? Compound Ksp Zn(OH)2 1.8 x 10-14 Fe(OH)2 1.1 × 10-14 A) The Ksp of Zn(OH)2 is greater, allowing more solid to dissolve. B) The Ksp of Fe(OH)2 is smaller, so its molar solubility is lower. C) Zn(OH)2 acts as an acid and neutralizes the NaOH, while Fe(OH)2 cannot neutralize the NaOH. D) Due to the common ion effect, the Zn(OH)2 equilibrium shifts to the right while the Fe(OH)2 equilibrium shifts to the left.

Chose A because C doesn't seem right because Zn and Fe are metals and positively charged. So they are similar in composition, they should do the same thing. D, common ion effect, because there is OH ion in the solution aready, it's gonna be hard for both of them to deissolve. However, the Ksp are not that different, but had no better choice. TEST: G-chem - solubility LEARN: The solubility of a compound increases as Ksp for that compound increases. However, A and B don't directly answer the question When excess hydroxide reacts with solid Zn(OH)2 it forms a new soluble coordination compound: Zn(OH)₄ C

TEST 1 9. Which of the following best explains the observed difference in electron affinity between chlorine and fluorine? A) Fluorine has a smaller atomic volume than chlorine, resulting in weaker repulsive forces between the existing electrons and the electron being added. B) Fluorine has a greater atomic volume than chlorine, resulting in weaker repulsive forces between the existing electrons and the electron being added. C) Fluorine has a smaller atomic volume than chlorine, resulting in stronger repulsive forces between the existing electrons and the electron being added. D) Fluorine has a greater atomic volume than chlorine, resulting in stronger repulsive forces between the existing electrons and the electron being added. electron affinities for fluorine and chlorine are -328 kJ/mol and -349 kJ/mol

Chose B because thought radius increases from left to the right. So F had larger radius than Cl therefore weaker repulsive forces between the existing electrons. TEST: atomic trends LEARN: atomic radius gets larger from the right to left, because electronegativity increases from left to right therefore it pulls on the electrons more so the radius is smaller. C

TEST 2 bio 56. aA+bB<->cC+dD The equilibrium constant for the reaction shown above can be expressed in terms of rate constants using the following equation: Keq=Kf/Kr where kf is the rate constant of the forward reaction, and kr is the rate constant of the reverse reaction. This assumes that: A) the forward and reverse rates are not equal. B) the reaction is a gaseous equilibrium. C) A and B react in a 1:1 ratio. D) the reaction is an elementary step.

Chose B. A is not right. C there is no indication of that. Didn't know what an elementary step is. But this is definitely in equilibrium. TEST: equilibrium LEARN: An elementary step has 0 intermediates, 1 transition state D

TEST 2 14. Another way to monitor urea degradation is by using phenolphthalein (pKa = 9.3), an indicator (In) that dissociates and changes color according to the following equation: Hln(clear) -> H⁺+ln⁻(magenta) Which of the following best explains why the solution turns magenta as urea degradation proceeds in the presence of phenolphthalein? A) Kb of NH3 > Ka of H2CO3 B) Ka of H2CO3 > Kb of NH3 C) Ka of NH4+ > Kb of HCO3- D) Ka of NH3 < Kb of H2CO3 (NH2)2CO, is degraded in solution via the following mechanism: Step 1: (NH2)2CO(aq) + H2O(l) -> CH3NO2(aq) + NH3(aq) Step 2: CH3NO2(aq) + H2O(aq) -> NH3(aq) + H2CO3(aq)

Concept - Acid and base Thought if indicator changes color then the pH must be greater than or around 9.3. Ka of H2Co3>Ka of NH3, Ka=1/Kb. Kb must be small. Dont know the logic for this. Ka and Kb are dissociation constants. If you want more basic stuff, you need more OH ions in the solution, which makes Kb more prevalent. A

TEST 1 55. The standard reduction potentials (E°) of Cl2 and Na+ are 1.36 V and -2.71 V respectively. What is the standard free energy change in the following reaction (F = 96,485 C/mol e-, 1 V = 1 J/C)? Cl2 + 2Na → 2NaCl A) 285 kJ/mol B) 772 kJ/mol C) -285 kJ/mol D) -772 kJ/mol

Concept - Electrochem Chose C because CL gains an electron getting reduced, reduction potential is 1.36V. Na loses electron, the oxidation potential is 2.71V. 1.36+2.71=4.07V. Convert it to 4J/C. times 96,485C/mol, and divide by 2 mol of e-. Comes down to C. Not sure if it's favorable or not. TEST: calculation LEARN: ΔG° = -nFE° ΔG° = -(2)(105)(4) = -8 × 105 J. got wrong on the 2 mol of e- should multiple by 2 D

TEST 1 41. What is the most likely reason why 226Ra is no longer used in household smoke detectors? A) Its decay product is a hazardous gas. B) It limits the useful lifespan of a smoke detector. C) Its decay mode is extremely harmful to humans. D) It results in alpha particle accumulation on the negative plate. Element Half Life Decay mode 241Am 432.2 years α 63Ni 100.1 years β- 226Ra 1602 years α

Concept - Radioactivity Chose B. Eliminated A and C. A because it decays to Rn. Thought Rn is inert, therefore it's not hazardous. C is not right becasue some smoke detects use alpha decay as well. D alpha particles don't accumulate on the plate. TEST: LEARN:

TEST 1 43. Which of the following is true regarding 63Ni decay? A) It decreases the number of protons because it has too many protons. B) It increases the number of protons because it has too many neutrons. C) It decreases the number of neutrons but the number of protons stays the same. D) It increases the number of protons but the number of neutrons stays the same. Element Half Life Decay mode 241Am 432.2 years α 63Ni 100.1 years β- 226Ra 1602 years α

Concept - Radioactivity Chose C because remembered that beta decay reduces mass. TEST: beta decay LEARN: β- loses one proton ⁰₋₁ B⁻ upper: mass of protons and neutrons lower: number of protons In beta decay, an unstable nucleus with too many neutrons attempts to become more stable by converting a neutron to a proton and emitting an electron. Go over decays and atomic number protons B

TEST 1 10. Which of the following elements is the least likely to undergo a displacement reaction with Na2S? A) O2 B) Cl2 C) K D)Li F2(aq) + 2 KI(aq) 2 KF(aq) + I2(aq) F2 > Cl2 > O2 > Br2 > I2

Concept - Redox Chemistry Chose C because to undergo displacement reaction, the element must have the reactivity less than S. A and B are eliminated. TEST: Analysis based on the reaction given LEARN: Reactivity of metals increases going down a group. Because metals have positive charge, so it loses an electron. The more likely it is to lose an electron more reactive it is. The atomic radius increases from low to high, so less attractive of the electrons, more likely to lose an electron D

TEST 2 15. Which of the following is true regarding the hydroxyl (-OH) group bridging the two nickel centers in the active site of urease? A) The pKa of the bridging hydroxyl is roughly the same as the pKa of methanol. B) The pKa of the bridging hydroxyl is higher than the pKa of methanol. C) The pKa of the bridging hydroxyl is lower than the pKa of methanol. D) The relationship between the pKa of methanol and of the bridging hydroxyl cannot be determined with the given information.

Concept - acid and base Chose B. Because Thought Methanol's OH group is connected to a Carbon atom. Ni is not as electronegative as carbon. So Ni is contributing electrons to the H on OH. Therefore H is not as acidic as the H in methonol. pKa of OH is higher than methanol. TEST: Acid and base LEARN: positive charge is more acidic, conjugate base is more stable, the stronger the acid another ex) H₃CS⁺H2, H₃CO⁺H₂, H₃CN⁺H₃ nitrogen is better at stablizing positive charge, so the acid is more stable than Sulfur, therefore weak acid. C

TEST 2 4. When dissolved in water, Cu2+ often forms the complex [Cu(OH2)6]2+. Which of the following is NOT true regarding this complex? A) The Cu2+ ion is weakly bound to the oxygen atom in the surrounding water molecules. B) The oxidation state of the copper is +2. C) The oxygen in the water acts as a Lewis base. D) The hydrogen in the water acts as a Lewis acid.

Concept - acid and base, oxidation state Chose C because at the end chose the one that is right. Thought oxygen was the donner and Cu was the acceptor. Forgot about it was asking for what is not true. TEST: lewis acid and base LEARN: lewis acid - electron acceptor, lewis base - electron donner In complex ions, Cu is the acceptor and O is the donner.

TEST 2 2. The chemist uses a concentration cell containing 0.1 M CuSO4 in the left half-cell and an unknown concentration of CuSO4 in the right half-cell. If she measures a potential of 0.030 V and can tell by the solution color that the unknown half-cell is more dilute, what is [Cu2+] in the unknown cell? A) 0.050 M B) 0.032 M C) 0.010 M D) 0.0010 M E = E°-0.059/n([diluteion]/[concentrated ion]) Concentration cells (Figure 1) generate potential from a difference in concentration of the same ion in two half-cells. For example, if one half-cell contains 1.5 M Cu2+ and a second contains 0.5 M Cu2+ Cu2+(aq) + 2e- Cu(s) 0.34 V

Concept - electrochemistry Chose D got wrong because thought E° is 0.34. Did the math wrong. TEST: concentration cell LEARN: For concentration cell, E° is 0 because same kind of chemical is being used. Ecell = Eoxidation + Ereduction C

TEST 1 16. SO₂(g) +1/2 O₂(g) -> SO₃ (g), Kp= 1.88 (at 1000 K). A reaction vessel at 1 atm total pressure and 1000 K contains 3 moles of SO2, 2.5 moles of O2, and 4.5 moles of SO3. For these conditions: A) ΔG = 0. B) ΔG is positive for the forward reaction. C) ΔG is negative for the forward reaction. D) ΔG = Keq.

Concept - equilibrium chose C because didn't know what moles will do to the equilibrium. dG=-RTlnK. If there are more moles of reactants, then it should shift forward. so forward reaction is more favorable. TEST: equilibrium LEARN: it the reaction is proceeding in a specific direction then the dG for that the favorable direction is<0, calculate Q can substitute K with Q B

TEST 2 Bio 11. One analytical tool for determining the amount of iron in blood is to treat the blood with cyanide ion, which complexes with the Fe2+ in hemoglobin and displaces the porphyrin to form the hexacyanoferrate(II) complex ion, [Fe(CN)6]4-. Which of the following statements supports the use of this method as a quantitative way of determining the iron concentration? A) The formation constant (Kf) of the [Fe(CN)₆]⁴⁻ ion is much larger than that of the Fe²⁺-hemoglobin complex. B) The Fe²⁺-hemoglobin complex and the [Fe(CN)₆]⁴⁻ ion can exist in equilibrium at similar concentrations. C) The formation constant (Kf) of the Fe²⁺-hemoglobin complex is much larger than that of the [Fe(CN)₆]⁴⁻ ion. D) The cyanide ion is a Lewis acid, making it an excellent ligand for complex ion formation.

Concept - formation constant in measuring Chose B. Eliminated C and D. Thought if formation constant is way greater than hemoglobin complex then the patient would be having problems transporting oxygen, which shouldn't happen during a test. TEST: quantitative way of measuring LEARN: Quantitative way we want to measure how much is in the blood. We want to react everything. A

TEST 2 47. Using Dalton's law, which of the following is the correct equation to determine the partial pressure of a component, Py, based on the concentration in parts per million, Cy? A) Py = (PtotalCy)(106) B) Py = (Ptotal / Cy)(106) C) Py = 106 / (PtotalCy) D) Py = (PtotalCy) / 106

Concept - gas calculation Chose A because thought Cy is in parts per million, to get the part then you have to time a million. TEST: parts per million calculation and dalton partial pressure law. LEARN: part/million=X (1000,000) X=ppm/10⁶ D

TEST 1 8. In an attempt to speed up her experiment, the researcher runs her reactions at 50°C rather than 25°C. However, this decreased the reaction rates. Which of the following best explains this result? A) The increased temperature decreased the average energy of the molecules in solution. B) The increased temperature reduced the solubility of the gas being bubbled through the solution. C) The increased temperature reduced the solubility of the ionic solid in aqueous solution. D) The reactions are exothermic. In a displacement series, a nonmetal gas is bubbled through a solution containing an aqueous ionic compound.

Concept - kinetic Chose D because increase temperature increase solubility of the gas and should increase the average energy of the molecules in solution. Reduced to C and D. Thought increase temperature will increase solubility in general. TEST: Kinetics LEARN: Increasing temperature decreases the solubility of gases in liquids. Maybe think of it as increase temp decreases orderliness so the gas molecules want to get free. Be sure to distinguish between theromdynamics and kinetics. Because the solubility of solids in liquids increases with increasing temperature. B

TEST 1 44. How will a smoke detector behave if it were exposed to an environment composed of fluorine and neon rather than nitrogen and oxygen? A) It will be less sensitive since fluorine and neon have higher ionization energies. B It will be less sensitive since fluorine and neon have lower ionization energies. C) It will be more sensitive since fluorine and neon have higher ionization energies. D) It will be more sensitive since fluorine and neon have lower ionization energies. because smoke particles attach to the ions and neutralize them.

Concept - periodic trends Chose A N2 and O2 lose electron being oxidized, Fluorine and neon are harder to lose electron because neon is stable and fluorine is more likely to gain an electron. So ionization e is high for F and Ne. TEST: Atomic trends LEARN: reason from the info presented in the passage harder to detect if there are 100 ions between the plates, because need more molecules of smoke to neutralize. C

TEST 2 38. The volume of a real gas under any set of conditions is smaller than the volume of an ideal gas under the same conditions. This is true because: A) the intermolecular forces of real gases are stronger than those of ideal gases. B) the volume of real gas particles is significant and reduces the free space in the vessel. C) the electron clouds of ideal gas particles repel each other more strongly than those of real gases. D) the intermolecular forces of ideal gases are stronger than those of real gases.

Concept- gas Chose A because ideal gases are mostly inert, so there is not that much interaction. Thought B said insignificant. TEST: ideal gas and real gas LEARN: volume of gas is the free space within the container Intermolecualr forces refer to pressure not volume B

TEST 2 3. If an experimenter measures a voltage of 0.09 V in a concentration cell at 25°C, what would the voltage of that same cell be if the temperature were raised to 300°C? A) 0.09 V B) 0.17 V C) 1.08 V D) Cannot be determined from the information given. E=E°-(RT/nF) ln Q

Didn't figure out that E° was 0. Didn't know the conversion for Calvin, thought if converted them they would still differ by a lot. TEST: Be able to predict changes LEARN: +273 Ecell = Eoxidation + Ereduction C

TEST 1 7. Which of the following best explains why F₂ is higher than Cl₂ in the reactivity series? A) F2 is more electronegative than Cl2. B) F2 has a more negative electron affinity than Cl2. C) Cl2 has a more positive reduction potential than F2. D) F2 has a more negative (SE)° than Cl2. ΔG° = EA + Δ(SE)° where EA is the electron affinity, and Δ(SE)° is the difference in solvation energies between the element with and without an added electron as shown in Equation 2. Δ(SE)° = (solvation energy X-)° - (solvation energy X)°

analysis with info from the passage Chose A because F₂ accepts an electron more readily than Cl₂. And I thought it was because of electronegativity because it attracts electrons. B and C are the same, not sure what D is suggesting. TEST: R LEARN: definiton of eletronegativty Electronegativity refers to behavior within a covalent bond and not in a reaction between molecules. If the Δ(SE)° is more negative for F2, the overall ΔG° is more negative indicating it is more energetically favorable to add an electron to F2 compared to Cl2. D