ACT science practice test 82

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.

Three substances have been shown to inhibit respiration in various organisms: hydrocyanic acid, hydrogen sulfide, and carbon monoxide. An experiment was conducted to determine the effect that each of these substances has on the respiration of the green alga Chlorella. Figure 1 shows the results.


Figure 1

Researcher 1 argued that glucose would have a contradictory effect on the alga, so that if the Chlorella were suspended in a solution containing 1 percent glucose, there would be less of an effect on respiration. Figure 2 displays the results of the experiment.


Figure 2

Researcher 2 hypothesized that light may play an active part in respiration of Chlorella, so an experiment was done to measure the effect of successive periods of light and darkness on the respiration of cells suspended in carbon monoxide and in nitrogen. The results are shown in Figure 3.


Figure 3

1. The theories of the two researchers are similar in that both researchers believe that:

F. glucose will increase the respiration of Chlorella.
G. HCN and H2S have no effect on the respiration of Chlorella.
H. an additional factor will have an effect on the respiration of Chlorella.
J. CO and N also affect the respiration of Chlorella.

2. According to Figure 1, Chlorella would typically consume about how much oxygen after half an hour?

A. 10 mm3
B. 18 mm3
C. 22 mm3
D. 35 mm3

3. If Researcher 1 was correct about the effect of glucose on the respiration of Chlorella, then based on the information in Figure 2, Researcher 1 would most likely predict that Chlorella suspended in a solution containing 2 percent glucose and HCN would consume how much oxygen after 20 minutes?

F. 15 mm3
G. 25 mm3
H. 30 mm3
J. 40 mm3

4. Does the data in Figure 3 support Researcher 2’s hypothesis?

A. Yes. It shows that light is necessary for the respiration of Chlorella.
B. Yes. It shows that equal respiration occurs in the darkness and in light.
C. No. More respiration of Chlorella occurred in the darkness.
D. No. Varying the amount of light did not yield significantly different rates of respiration.

5. Suppose a third researcher studied the effect of glucose and CO on the respiration of Chlorella, using the same conditions and methods as Researcher 1. After 20 minutes the results showed that the sample suspended in CO had consumed 50 mm3 of oxygen, while the sample suspended in a mixture of CO and glucose had consumed 60 mm3 of oxygen. How would this experiment most likely affect the researchers’ viewpoints?

F. It would weaken Researcher 2’s viewpoint only.
G. It would weaken Researcher 1’s viewpoint only.
H. It would strengthen both researchers’ viewpoints.
J. It would have no effect on either researcher’s viewpoint.

6. According to Figure 2, which substance had the LEAST effect on respiration of Chlorella after 30 minutes?

B. H2S
C. Glucose + HCN
D. Glucose + H2S

7. According to Researcher 2, experiment findings indicate the following is FALSE regarding the relationship between Chlorella cells suspended in carbon monoxide and Chlorella cells suspended in nitrogen EXCEPT:

F. Chlorella cells suspended in carbon monoxide consume more oxygen.
G. Chlorella cells suspended in nitrogen consume less oxygen.
H. Chlorella cells suspended in carbon monoxide and nitrogen consume the same amount of oxygen.
J. Chlorella cells suspended in nitrogen consume more oxygen.

A catalyst is a substance that speeds up a reaction, but is chemically unchanged at the end of the reaction. Catalysts can be divided into two main types—heterogeneous and homogeneous. In a heterogeneous reaction, the catalyst is in a different phase (such as solid, liquid, or gas) from the reactants. In a homogeneous reaction, the catalyst is in the same phase as the reactants. Most examples of heterogeneous catalysis go through the same stages (see Table 1).

Table 1




One or more of the reactants are absorbed onto the surface of the catalyst.


There is some sort of interaction between the surface of the catalyst and the reactant molecules, which makes them more reactive.


The reaction happens.


The product molecules are desorbed, meaning that the product molecules break away.

Students did experiments to convert propanol to propene using alumina beads, and then to convert propene to propanol using a palladium catalyst.

Experiment 1

Two glass syringes were connected to an aluminabead catalyst tube (see Figure 1). The 1 mL syringe was filled with 1 mL of propanol. Next, the apparatus was held above a burner’s flame and the alumina-bead catalyst tube was gently heated while the liquid propanol was slowly introduced into the catalyst tube. The liquid flowed through the tube until it hit the hot region. Then it vaporized, reacted with the catalyst, and exited the catalyst tube as gaseous propene into the 60-mL receiver syringe. The procedure was repeated with various amounts of propanol and alumina beads and the amount of gaseous propene collected was recorded (see Table 2).


Figure 1

Table 2


Experiment 2

A reactant syringe was filled with equal volumes of hydrogen and propene. The reactant syringe and receiver syringe were connected to the catalyst tube filled with solid palladium as shown in Figure 2. Then the hydrogenpropene mixture was slowly passed over the catalyst, the reaction occurred, and the propane was collected in the receiver syringe. The procedure was repeated several times, varying the amount of time the reactant was passed over the catalyst. The results are shown in Table 3.


Figure 2

Table 3


8. In Experiment 2, as the amount of time the reactant was passed over the catalyst decreased, the volume of propane created:

A. increased only.
B. decreased only.
C. increased and then remained constant.
D. decreased and then remained constant.

9. Which is the most likely explanation for why 0 mL of propane was produced in Trial 4 of Experiment 2?

F. There was not enough volume of hydrogen and propene to create a reaction.
G. Fifteen seconds was too long a time for the reactant to pass over the catalyst.
H. There was not enough volume of palladium in the catalyst tube to create a reaction and produce propane.
J. The reactant was not allowed enough time to interact with the catalyst; therefore no reaction occurred and no propane was produced.

10. What type of catalyst was used in Experiment 1?

A. It cannot be determined from the information given.
B. A liquid catalyst
C. A heterogeneous catalyst
D. A homogeneous catalyst

11. In Experiment 2, the hydrogen-propene mixture turns into propane at what stage of the catalysis?

F. Stage 1
G. Stage 2
H. Stage 3
J. Stage 4

12. Based on the data in Table 2, which two trials illustrate the effect that varying the volume of the catalyst has on the volume of propene produced?

A. Trials 1 and 2
B. Trials 1 and 3
C. Trials 3 and 4
D. Trials 2 and 4

13. Which of the following best describes what occurred to the plunger of the 60-mL syringe during Experiment 1? When propanol was injected into the catalyst tube, the distance between the end of the plunger and the syringe tip:

F. decreased slowly over 30 seconds.
G. increased immediately, and then decreased as the reaction occurred.
H. remained in place until the reaction occurred, and then decreased.
J. remained in place until the reaction occurred, and then increased.