SAT Subject Test Chemistry

PART 2

REVIEW OF MAJOR TOPICS

CHAPTER 15

The Laboratory

Practice Exercises

Practice Exercises

1. In the reaction setup shown above, which of the following are true?

  I. This setup can be used to prepare a soluble gas by water displacement.

 II. This setup involves a decomposition reaction if the substance heated is potassium chlorate.

III. This setup can be used to prepare an insoluble gas by water displacement.

(A) I only

(B) II only

(C) I and III

(D) II and III

(E) I, II, and III

Questions 2–4 refer to the following diagram:

(A) Around the thermometer

(B) In the condenser

(C) In the circulating water

(D) In the heated flask

(E) In the distillate

2. In this laboratory setup for distillation, where does the vaporization take place?

3. If the liquid being distilled contains dissolved magnesium chloride, where will it be found after distillation is completed?

4. If the liquid being distilled contains dissolved ammonia gas, where will it be bound after distillation is completed?

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5. If the flame used to heat a flask is an orange color and blackens the bottom of the flask, what correction should you make to solve this problem?

(A) Move the flask farther from the flame.

(B) Move the flask closer to the flame.

(C) Allow less air into the collar of the burner.

(D) Allow more air into the collar of the burner.

(E) The problem is in the supply of the gas, and you cannot fix it.

Questions 6–8 refer to the following diagram:

6. In the above titration setup, if you introduce 15 mL of the NaOH with an unknown molarity into the flask and then add 5 drops of phenolphthalein indicator, what will you observe?

(A) A pinkish color will appear throughout the solution.

(B) A blue color will appear throughout the solution.

(C) There will be a temporary pinkish color that will dissipate.

(D) There will be a temporary blue color that will dissipate.

(E) There will not be a color change.

7. If the HCl is 0.1 M standard solution and you must add 30 mL to reach the end point, what is the molarity of the NaOH?

(A) 0.1 M

(B) 0.2 M

(C) 0.3 M

(D) 1 M

(E) 2 M

8. When is the end point reached and the volume of the HCl recorded in this reaction?

  I. When the color first disappears and returns in the flask.

 II. When equal amounts of HCl and NaOH are in the flask.

III. When the color disappears and does not return in the flask.

(A) I only

(B) III only

(C) I and III

(D) II and III

(E) I, II, and III

Questions 9–11 refer to the following diagram:

In this setup, a clean strip of magnesium with a mass of 0.040 g was introduced into the bottom of the tube, which contained a dilute solution of HCl, and allowed to react completely. The hydrogen gas formed was collected and the following data recorded:

Air pressure in the room = 730 mm Hg
    Temperature of the water solution = 302 K
    Vapor pressure of water at 302 K = 30.0 mm Hg

The gas collected did not fill the eudiometer. The height of the meniscus above the level of the water was 40.8 mm.

9. What is the theoretical yield (in mL) at STP of hydrogen gas produced when the 0.040 g of Mg reacted completely?

(A) 10 mL

(B) 25 mL

(C) 37 mL

(D) 46 mL

(E) 51 mL

10.   What is the correction to the atmospheric pressure due to the 40.8 mm height of the solution in the tube and above the level in the beaker?

(A) 3.0 mm Hg

(B) 6.0 mm Hg

(C) 13.6 mm Hg

(D) 27.2 mm Hg

(E) 40.8 mm Hg

11.   What is the pressure of the collected gas once you have also corrected for the vapor pressure of the water?

(A) 730 mm Hg

(B) 727 mm Hg

(C) 30.0 mm Hg

(D) 697 mm Hg

(E) 760 mm Hg

Questions 12–14

(A) The rule is to add concentrated acid to water slowly.

(B) The rule is to add water to the concentrated acid slowly.

(C) Carefully replace unused or excess chemicals into their properly labeled containers from which they came.

(D) Flush eyes with water at the eyewash fountain for at least 15 minutes, and then report the accident for further help.

(E) Dispose of chemicals in the proper places and following posted procedures. Do not return them to their original containers.

12.   Which of the above choices is the proper way to dilute a concentrated acid?

13.   How do you properly dispose of chemicals not needed in the experiment?

14.   What should you do if a chemical splatters into your eye?

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15.   What instrument is used in chemistry labs to measure the molarity of a colored solution by measuring the light transmitted through it?

(A) Electronic gravimetric balance

(B) pH meter

(C) Spectrophotometer

(D) Computer assisted probes

(E) Galvanometer

Answers and Explanations

1. (D) This setup can be used to prepare an insoluble gas but not a soluble one. If the substance is potassium chlorate, it does decompose into potassium chloride and oxygen.

2. (D) Vaporization occurs in the heated flask.

3. (D) The magnesium chloride will be left behind in the heated flask since it is not volatile as the liquid boils off.

4. (E) Since the dissolved ammonia is volatile below the boiling point of water, it will be found in the distillate. Some will also escape as a gas.

5. (D) One of the basic adjustments to a burner is to assure enough air is mixing with the gas to form a blue cone-shaped flame. With insufficient air, carbon deposits will form on the flask and the flame will be orange.

6. (A) Phenolphthalein indicator is colorless below a pH of 8.3 but is red to pink in basic solutions above this pH. In this NaOH solution, it will be red to pink.

7. (B) Calculate the molarity by using the formula:

Macid × Vacid = Mbase × Vbase
0.1 M × 30 mL = Mbase × 15 mL
Mbase = 0.2 M

Notice that as long as the units of volume are the same, they cancel out of the equation.

8. (B) The end point is reached when the color of the indicator disappears and does not return. The color will first disappear temporarily before the end point but finally will not return.

9. (C) The theoretical yield at STP can be found from the chemical equation of the reaction:

10. (A) The 40.8 mm of water being held up in the tube by atmospheric pressure can be changed to its equivalent height of mercury by dividing by 13.6, since 1 mm of Hg = 13.6 mm of water.

              

By correcting the atmospheric pressure, we get: 730 mm Hg - 3 mm Hg = 727 mm Hg

11. (D) Correcting the previous pressure by subtracting the given amount for the vapor pressure of water at 302 K gives you 727 mm Hg - 30 mm Hg vapor pressure = 697 mm Hg as the final pressure.

12. (A) The correct and safe way to dilute concentrated acids is to add water down the side of the beaker slowly and be aware of any heat buildup.

13. (E) You never return chemicals or solutions to their original containers for fear of contaminating the original source.

14. (D) It is essential to get your eyes washed of any chemicals. Know where the eyewash fountains are, and know how to use them.

15. (C) One of the new technological additions to chemistry labs is the spectron 20 that uses the absorption of light waves to do qualitative and quantitative investigations in the lab.