Ap chem 프린스턴 화학 summary part 9

Question 1:

In a Zn–Cu voltaic cell with [Cu²⁺] = 1.0 M and [Zn²⁺] = 1.0 M, the standard cell potential is 1.10 V. Which change will increase the cell potential above 1.10 V?

• (A) Decreasing [Cu²⁺] to 0.10 M while [Zn²⁺] remains 1.0 M
• (B) Decreasing [Zn²⁺] to 0.10 M while [Cu²⁺] remains 1.0 M
• (C) Keeping [Zn²⁺] and [Cu²⁺] both at 1.0 M
• (D) Lowering both [Zn²⁺] and [Cu²⁺] to 0.10 M

Question 2:

For the electrolysis of molten NaCl (2NaCl → 2Na + Cl₂), which statement is correct?

• (A) Na⁺ ions are reduced to Na metal at the cathode, and Cl₂ gas forms at the anode.
• (B) Cl⁻ ions are reduced at the cathode, producing Cl₂ gas.
• (C) The process is spontaneous and requires no external voltage.
• (D) Electrons flow from cathode to anode spontaneously.

Question 3:

Why is an external power source required in the electrolysis of molten NaCl?

• (A) Because the overall reaction is non-spontaneous (ΔG > 0), requiring input energy.
• (B) Because NaCl has a high boiling point that must be maintained.
• (C) To pump electrons with higher kinetic energy for faster deposition.
• (D) Because ΔH is positive and the process absorbs heat.

Question 4:

A student needs to prepare 100 mL of 1.00 M NaCl solution. Which procedure is correct?

• (A) Weigh 5.85 g NaCl, dissolve in water, and dilute to 100 mL in a volumetric flask.
• (B) Pour 100 mL of water into NaCl until fully saturated.
• (C) Weigh 1.00 g NaCl and dissolve it in exactly 100 mL of water.
• (D) Use any volume of NaCl and dilute until clear solution is obtained.

Question 5:

According to Beer’s Law (A = abc), if the concentration of a dye solution is doubled while keeping path length constant, what happens to the absorbance?

• (A) It decreases by half.
• (B) It remains constant.
• (C) It doubles.
• (D) It quadruples.

Question 6:

In paper chromatography with water as the solvent, substance D travels the farthest compared to A, B, and C. What does this indicate about substance D?

• (A) It has the strongest affinity for the stationary phase.
• (B) It is least soluble in water.
• (C) It has the greatest affinity for the mobile phase (water).
• (D) It reacts chemically with the solvent.

Question 7:

Which method would you use to separate a mixture of sand (insoluble) and dissolved salt in water?

• (A) Filtration to separate sand, followed by evaporation to obtain solid salt.
• (B) Distillation only.
• (C) Chromatography.
• (D) Filtration alone is sufficient for both.

Question 8:

A galvanic cell is built using a Zn electrode in 1.0 M Zn²⁺ solution and a Cu electrode in 1.0 M Cu²⁺ solution. Which statement is correct about this cell?

• (A) Electrons flow from the Cu electrode to the Zn electrode.
• (B) Zn is oxidized at the anode, and Cu²⁺ is reduced at the cathode.
• (C) The Cu electrode is the anode, and Zn²⁺ is reduced at the cathode.
• (D) No electron flow occurs because the two metals have the same potential.

Question 9:

Which of the following statements correctly explains why electrolysis is considered non-spontaneous?

• (A) Because the reaction requires heat input instead of electricity.
• (B) Because ΔG for the overall process is positive, requiring external electrical energy.
• (C) Because ions cannot move freely in molten salts.
• (D) Because the electrodes are consumed too quickly.

Question 10:

A student prepares 500 mL of 0.10 M H₂SO₄ using concentrated H₂SO₄. Which is the correct procedure?

• (A) Pour 25 mL of concentrated acid directly into 500 mL of water.
• (B) Add acid to water slowly in a volumetric flask until the volume reaches 500 mL.
• (C) Add water into concentrated acid carefully until 500 mL is reached.
• (D) Mix acid and water in any order as long as the ratio is correct.

Question 11:

During electroplating, which factor directly determines the mass of metal deposited on the cathode?

• (A) The size of the electrodes.
• (B) The current and the time of electrolysis (q = It).
• (C) The color of the electrolyte solution.
• (D) The atmospheric pressure during the process.

Question 12:

In a reactivity series test, metal X does not displace Y²⁺ from solution but displaces Z²⁺. Which is the correct order of reduction potential (from highest to lowest)?

• (A) Y²⁺ > X²⁺ > Z²⁺
• (B) X²⁺ > Y²⁺ > Z²⁺
• (C) Z²⁺ > Y²⁺ > X²⁺
• (D) X²⁺ > Z²⁺ > Y²⁺

Question 13:

In Beer’s Law (A = abc), which parameter represents the path length of the cuvette?

• (A) a
• (B) b
• (C) c
• (D) A

Question 14:

Which separation technique would best separate a liquid mixture of ethanol and water?

• (A) Filtration
• (B) Distillation based on boiling point differences
• (C) Paper chromatography
• (D) Evaporation to dryness

Question 15:

In a voltaic cell, why does the salt bridge contain both cations and anions?

• (A) To provide a source of additional reactants for the electrodes.
• (B) To maintain electrical neutrality in each half-cell as the reaction proceeds.
• (C) To increase the overall voltage of the cell.
• (D) To allow electrons to flow directly between the two half-cells.

Question 16:

In a voltaic cell, the anode is always the site of:

• (A) Oxidation
• (B) Reduction
• (C) Neutralization
• (D) Electron gain

Question 17:

Which factor does not affect the measured cell potential of a voltaic cell?

• (A) Concentrations of ions in each half-cell
• (B) Temperature of the system
• (C) The metal used as electrodes
• (D) The color of the electrode material

Question 18:

During electrolysis of molten MgCl₂, which products form at the cathode and anode?

• (A) Mg at the cathode, Cl₂ at the anode
• (B) Cl₂ at the cathode, Mg at the anode
• (C) H₂ at the cathode, O₂ at the anode
• (D) Only Mg forms at both electrodes

Question 19:

Which condition increases the likelihood of a spontaneous redox reaction between two metals?

• (A) A large difference in their reduction potentials
• (B) Identical reduction potentials
• (C) High temperature only
• (D) The use of inert electrodes

Question 20:

A salt bridge in a galvanic cell is necessary to:

• (A) Prevent mixing of the two solutions
• (B) Maintain electrical neutrality in each half-cell
• (C) Provide a pathway for electron transfer
• (D) Increase the measured voltage

Question 21:

In preparing a standard solution, why must the solute be completely dissolved before diluting to the mark?

• (A) To ensure the final concentration is accurate
• (B) To prevent bubbles forming in the flask
• (C) To avoid changing the solute’s color
• (D) To reduce the vapor pressure of the solvent

Question 22:

Which of the following is the best method to separate a mixture of oil and water?

• (A) Filtration
• (B) Decantation or separatory funnel
• (C) Distillation using a paper wick
• (D) Paper chromatography

Question 23:

If the concentration of Cu²⁺ in a Cu–Zn cell increases, what happens to the cell voltage?

• (A) It decreases
• (B) It increases
• (C) It remains the same
• (D) It drops to zero immediately

Question 24:

In Beer’s Law, which combination would cause absorbance (A) to increase?

• (A) Lower molar absorptivity and shorter path length
• (B) Higher concentration and longer path length
• (C) Lower concentration and shorter path length
• (D) Diluted solution in a thin cuvette

Question 25:

A student filters a mixture of sand and salt solution. What will be collected in the filtrate?

• (A) Only sand
• (B) Only pure water
• (C) Dissolved salt solution
• (D) Both sand and dissolved salt

Question 26:

In a galvanic cell, electrons always flow:

• (A) From cathode to anode through the external circuit
• (B) From anode to cathode through the external circuit
• (C) From salt bridge to electrodes
• (D) Randomly between both electrodes

Question 27:

Which process is used to obtain pure copper from impure copper using an electrolytic cell?

• (A) Electrorefining
• (B) Electroplating
• (C) Distillation
• (D) Chromatography

Question 28:

Which of the following statements correctly describes an electrolytic cell?

• (A) It produces electrical energy from a spontaneous reaction.
• (B) It requires an external power source to drive a non-spontaneous reaction.
• (C) It does not involve electron transfer.
• (D) It is identical in principle to a galvanic cell.

Question 29:

Why must a buret be rinsed with the titrant solution before starting a titration?

• (A) To prevent dilution of the titrant by residual water
• (B) To sterilize the glassware
• (C) To warm the buret for better flow
• (D) To reduce surface tension of the liquid

Question 30:

Which laboratory technique would best separate a solid precipitate from a liquid after a reaction?

• (A) Filtration
• (B) Distillation
• (C) Paper chromatography
• (D) Decantation

Question 31:

In a Zn–Cu voltaic cell, which statement is correct about the direction of ion flow through the salt bridge?

• (A) Cations flow into the Zn half-cell; anions flow into the Cu half-cell.
• (B) Cations flow into the Cu half-cell; anions flow into the Zn half-cell.
• (C) Only cations move between half-cells.
• (D) Only anions move between half-cells.

Question 32:

Which of the following laboratory practices ensures the most accurate concentration of a prepared standard solution?

• (A) Using a graduated cylinder to measure the solvent
• (B) Using a volumetric flask to dilute to the calibration mark
• (C) Using a beaker to approximate the final volume
• (D) Adding excess solvent for convenience

Question 33:

In a galvanic cell, which change would cause the cell voltage to decrease?

• (A) Increasing [Cu²⁺]
• (B) Decreasing [Cu²⁺]
• (C) Decreasing [Zn²⁺]
• (D) Using a larger salt bridge

Question 34:

Which factor directly influences the wavelength of maximum absorbance in a spectrophotometric experiment?

• (A) The identity of the solute (its electronic structure)
• (B) The path length of the cuvette
• (C) The concentration of the solution
• (D) The calibration of the balance used

Question 35:

Which of the following is the safest procedure when diluting concentrated sulfuric acid?

• (A) Slowly add acid to water with constant stirring
• (B) Slowly add water to acid with constant stirring
• (C) Add both together rapidly in a large beaker
• (D) Mix equal parts water and acid simultaneously