ACT Science Practice Test 112

Directions: Each passage is followed by several questions. After reading a passage, choose the best answer to each question and fill in the corresponding oval on your answer document. You may refer to the passages as often as necessary.

You are NOT permitted to use a calculator on this test.


PASSAGE VI

Certain preservatives known as sulfites are often added to fruit products to keep the fruit fresher longer. Use of sulfites is controversial because studies have linked sulfites to severe reactions in some asthmatics. Students performed 2 experiments to measure sulfite levels.

Experiment 1

Four solutions, each containing a different amount of sulfite dissolved in H2O were prepared. A coloring agent was added that binds with sulfite to form a red compound that strongly absorbs light of a specific wavelength, and each solution was diluted to 100 mL. A blank solution was prepared in the same manner, but no sulfite was added. A colorimeter (a device that measures how much light of a selected wavelength is absorbed by a sample) was used to measure the absorbance of each solution. The absorbances were corrected by subtracting the absorbance of the blank solution from each reading (see Table 1 and Figure 1).

Figure 1

Experiment 2

A 100 g fruit sample was ground in a food processor with 50 mL of H2O and the mixture was filtered. The food processor and remaining fruit were then washed with H2O, these washings were filtered, and the liquid was added to the sample solution. The coloring agent was added and the solution was diluted to 100 mL. The procedure was repeated for several fruits, and the absorbances were measured (see Table 2).

1. Based on the results of Experiment 1, if the concentration of sulfite in a solution is doubled, then the corrected absorbance of the solution will approximately:

A. remain the same.
B. halve.
C. double.
D. quadruple.

2. A sample of dried pineapple was also measured in Experiment 2 and its corrected absorbance was determined to be 0.603. Which of the following correctly lists prunes, apricots, and dried pineapple in decreasing order of corrected absorbance?

F. Prunes, dried apricots, dried pineapple.
G. Dried pineapple, apricots, prunes.
H. Prunes, dried pineapple, dried apricots.
J. Dried apricots, dried pineapple, prunes.

3. Based on the results of Experiment 1, if a solution with a concentration of 1.5 ppm sulfite had been tested, the corrected absorbance would have been closest to which of the following values?

A. 0.160
B. 0.240
C. 0.300
D. 0.360

4. If Experiments 1 and 2 were repeated using a different coloring agent that produces a different color when it binds with sulfite, which of the following changes in procedure would be necessary?

F. The new coloring agent should be added to the blank solution, but not to the sample solutions.
G. Both of the coloring agents should be added to the blank solution and to all of the samples.
H. The absorbance of the blank solution made with the new coloring agent should be added to the measured absorbances.
J. The colorimeter should be set to measure at a different wavelength of light.

5. Based on the results of Experiments 1 and 2, if the measured absorbances for the fruits tested in Experiment 2 were compared with their corrected absorbances, the measured absorbances would be:

A. higher for all of the fruits tested.
B. lower for all of the fruits tested.
C. lower for some of the fruits tested, higher for others.
D. the same for all of the fruits tested.

6. If some of the water-soluble contents found in all of the fruits tested in Experiment 2 absorbed light of the same wavelength as the compound formed with sulfite and the coloring agent, how would the measurements have been affected? Compared to the actual sulfite concentrations, the sulfite concentrations apparently measured would be:

F. higher.
G. lower.
H. the same.
J. higher for some of the fruits, lower for others.