5 STEPS TO A 5: 500 AP Chemistry Questions to Know by Test Day! (2012)

429. Which of the following is an acceptable laboratory practice?

(A) Placing hot objects on a balance

(B) Diluting a solution in a volumetric flask with hot water

(C) Using 5 mL of phenolphthalein to titrate 20 mL of an acidic solution

(D) Adding water slowly to a preweighed solid acid in a dry Erlenmeyer flask

(E) Rinsing a burette with a standardized solution before filling it with the standardized solution

430. The proper procedure for the dilution of concentrated NaOH is to slowly add the base to a beaker of water rather than slowly adding water to the beaker of base. This precaution is to ensure that

(A) there is sufficient time for the full ionization of NaOH.

(B) the water does not float on top of the denser base and remain unmixed.

(C) the base does not react with the dry beaker or impurities in the beaker.

(D) there is a enough water to absorb the heat released.

(E) there is enough water for the OH⁻ ions to be completely dissolved.

431. A student accidentally splashes a concentrated, strong acid onto his bare skin. Which of the following is the safest and most effective course of action?

(A) Dry the skin with paper towels.

(B) Flush the area with water and a dilute solution of a weak acid.

(C) Flush the area with a dilute NaOH solution, then water.

(D) Flush the area with water and then a dilute solution of NaHCO₃.

(E) Sprinkle the area with powdered Na₂SO₄, then carefully shake off the excess and rinse with water.

432. A student dissolves a 20.0 mol sample of acetic acid, a weak acid, into 1 kg of water to make a 20.0 molal solution. Assuming no other information is available to the student, which of the following is the best way to determine the molarity of the solution?

(A) Titrate with a standard acid

(B) Measure the total volume of the solution

(C) Determine the freezing point of the solution

(D) Measure the pH with a calibrated pH meter

(E) Measure the electrical conductivity of the solution

433. A 98-gram sample of phosphoric acid, H₃PO₄ (a weak acid), is dissolved in 1 kg of water. Assuming no other information is available, which of the following procedures is the best way to determine the molarity of the solution?

(A) Measure the total mass of the solution

(B) Measure the total volume of the solution

(C) Measure the pH of the solution with a calibrated pH meter

(D) Determine the boiling point of the solution

(E) Titrate the solution with a standard acid

Questions 434–438 refer to the following answer choices:

(A) Visible-light spectrophotometry (colorimetry)

(B) Paper chromatography

(C) Titration

(D) Gravimetric determination or differential precipitation

(E) Electrodes

434. Can be used to measure the conductivity of a solution

435. Used to separate pigments in a mixture

436. Used to determine the concentration of a solution of KMnO₄

437. Used to determine if Na⁺, Mg²⁺, and/or Pb²⁺ ions are present in a solution

438. Used to determine the unknown concentration of a known reactant

439. Which of the following procedures would allow a student to boil water at a temperature significantly above 100°C in a laboratory in which the temperature is 22°C and the pressure is 1 atm?

(A) Add salt to the water

(B) Stir or agitate the water as it is heating

(C) Insulate and cover the container in which the water is heated

(D) Heat the water in a sealed container into which air has been pumped to increase the pressure in the container

(E) Heat the water in a sealed container from which all the atmospheric air has been removed

440. Which of the following measures of concentration changes with temperature?

(A) Mole fraction

(B) Mass fraction

(C) Mass percentage

(D) Molality

(E) Molarity

441. Which of the following pieces of laboratory glassware would be used to most accurately transfer a 10.00-mL sample of solution?

(A) 5-mL pipet

(B) 10-mL pipet

(C) 10-mL graduated cylinder

(D) 15-mL graduated cylinder

(E) 15-mL Erlenmeyer flask

442. A student determined the density of a pure liquid at 25°C by measuring its mass with an electronic balance and measuring its volume in a clean, dry 50.00-mL volumetric flask. On the basis of this information and the measurements shown in the table below, to how many significant digits should this density be reported?

(A) 2

(B) 3

(C) 4

(D) 5

(E) 6

443. A student weighs out 0.20 mol of glucose to prepare a 2-M glucose solution. Which of the following pieces of laboratory equipment is most appropriate for preparing this solution?

(A) 100-mL graduated cylinder

(B) 1-L graduated cylinder

(C) 1-L Erlenmyer flask

(D) 100-mL volumetric flask

(E) 1-L volumetric flask

444. Which of the following techniques is most appropriate for recovering solid NH₄NO₃ from an aqueous solution of NH₄NO₃?

(A) Thin layer chromatography

(B) Evaporation

(C) Distillation

(D) Filtration

(E) Titration