ACT Science : Chemistry
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Example Questions
Example Question #41 : Chemistry
A scientist decided to use high-tech equipment to measure the electronegativity, an atom's attraction to electrons, of the second period on the periodic table. The results of her measurements are in the chart below. Z is equal to the atomic number of the specified atom and the number of protons in that atom.
According to the experimenter's measurements, what is the apparent relationship between number of protons and the electronegativity of an atom?
Negative linear relationship
There is no clear relationship
Negative exponential relationship
Positive exponential relationship
Positive linear relationship
Positive linear relationship
The correct answer is that it is a positive linear relationship. We can see that as we increase one proton, the electronegativity tends to increase consistently by about 0.5 Debyes.
Example Question #42 : Chemistry
A scientist decided to use high-tech equipment to measure the electronegativity, an atom's attraction to electrons, of the second period on the periodic table. The results of her measurements are in the chart below. Z is equal to the atomic number of the specified atom and the number of protons in that atom.
What is the apparent relationship between an atom's atomic number Z and its likelihood to attract electrons from a source of electrons?
Lower atomic number indicates a lower likelihood of attracting electrons
Lower atomic number indicates a higher likelihood of attracting electrons
Higher atomic number indicates a lower likelihood of attracting electrons
There is no discernible relationship
Higher atomic number indicates a higher likelihood of attracting electrons
Higher atomic number indicates a higher likelihood of attracting electrons
As defined in the passage, higher electronegativity implies a greater ability to attract electrons. Therefore, we can discern that there is a direct relationship between the two variables. As one goes up, so does the other.
Example Question #43 : How To Find Data Representation In Chemistry
Solutions are made by dissolving a solute into a solvent. Different types of solvents have varying levels of solubility, or ability to dissolve certain substances.
A student decided to conduct an experiment to compare the solubilities of different solvents at different temperatures using table salt (sodium chloride) as a solute. The student would keep an amount of solvent at the specified temperature and add solute until no more solute would dissolve. This is amount or solute is called the point of saturation. The amount added to each solvent at saturation was recorded. The results of the experiment are shown in the tables:
Table 1:
Table 2:
Based on the data, which solvent involved in the experiment has the greatest solubility?
Dichloromethane
Ethanol
Hexane
Water
More information is necessary
Water
The correct answer is water. We see that at both temperatures, water is able to dissolve more salt than the other solvents. Therefore, it has the highest solubility.
Example Question #44 : How To Find Data Representation In Chemistry
A free energy reaction diagram shows the energy of a chemical reaction as it progresses from start to finish. In Example 1 below, the reactants (at point A) start with a certain energy. Energy is then applied to initiate the reaction (this is called activation energy) and the reaction progresses to point B. Lastly, energy is released in the reaction leading to point C. If the net change in free energy of a reaction is positive, the reaction is called a nonspontaneous reaction, meaning that it takes more energy to initiate it than the energy released. If the net change in free energy of a reaction is negative, it is called spontaneous, meaning that the energy released is more than the energy needed to initiate the reaction.
Example 1:
What can we conclude about Example 1 above given the information in the passage?
The net change of the free energy is negative
The reaction is spontaneous
The reaction releases more energy than is required to initiate it
The reaction is nonspontaneous
The activation energy is negative
The reaction is nonspontaneous
The correct answer is that it is nonspontaneous. As the energy at the end of the reaction is higher than where it began, we know that the net change in energy was positive. Therefore, according to the information in the passage, the reaction is nonspontaneous.
Example Question #41 : Chemistry
Solutions are made by dissolving a solute into a solvent. Different types of solvents have varying levels of solubility, or ability to dissolve certain substances.
A student decided to conduct an experiment to compare the solubilities of different solvents at different temperatures using table salt (sodium chloride) as a solute. The student would keep an amount of solvent at the specified temperature and add solute until no more solute would dissolve. This is amount or solute is called the point of saturation. The amount added to each solvent at saturation was recorded. The results of the experiment are shown in the tables:
Table 1:
Table 2:
What is the apparent relationship between temperature and solubility?
Direct, exponential relationship
No discernible relationship
Direct, linear relationship
Direct relationship
Inverse relationship
Direct relationship
This is a tricky question because it not only involves identifying the apparent positive correlation between temperature and solubility (amount of solute dissolved at saturation), but it also involves recognizing that we do not have enough information to determine whether the relationship is exponential or linear.
First, we see that as we increase the temperature, the amount of solute that can dissolve at saturation increases. This tells us that there is a direct relationship. However, to determine with certainty whether the relationship is exponential or linear, we would need another set of data showing whether the increases themselves were increasing. That is, at a proportionally higher temperature than 35 degrees Celsius, whether or not the increase in solubility would be the same as the first temperature increase.
Therefore, the answer is that there is a direct relationship.
Example Question #41 : Chemistry
A chemist has mixed up the labels on some of his chemical compounds. To try to determine the compounds, the chemist dissolves the compounds in pure water. He notes the pH, corrosiveness and the color of each solution.
Assume that all of the substances can clean surfaces. Which of the substances will clean most surfaces without wrecking the surface?
C and B
B only
A and C
A and B
B and D
A and C
Corrosive substances can destroy the surface of whatever is being cleaned. The chemist wants to select the solutions that are not corrosive, which are solutions A and C.
Example Question #41 : Chemistry
If a drug is taken orally, then the concentration of that drug in the blood will rise to a peak concentration. Immediately afterwards, the elimination phase begins and the concentration of the drug in the body will fall exponentially. Each drug has a half-life (i.e. the time required for the drug's concentration in the blood to fall to half of its original value). Once the elimination phase has initiated, it typically takes four half-lives until the drug has been entirely eliminated from the body.
If an individual is given multiple doses of a drug over time, then the blood concentration of the drug will rise and fall periodically. This creates a graph of drug’s concentration versus time that will resemble a wave. The rising peaks of the graph occur immediately after administration of a dose, whereas the falling valleys occur as the drug is being eliminated. The inter-dose interval, represented by the letter 
Experiment 1
A 125-milligram oral dose of a drug known as Cyclosporin A (CsA) was administered to an individual. The CsA blood concentration for this individual was then measured at various times over the next 24 hours. A graph of CsA concentration versus time was obtained.
Experiment 2
An individual was given multiple doses of CsA over a 60-hour period. The CsA blood concentration was monitored continuously. A graph of CsA concentration versus time was obtained.
Based on the results of Experiment 2 and information in the passage, what was the inter-dose interval of CsA?
The inter-dose interval is defined as the time (in hours) between doses of the drug. The passage states that rising portions of the graph occur immediately after administration of a dose. Since rising portions begin at 12, 24, 36, and 48 hours, we can conclude that the inter-dose interval is as follows:
Example Question #731 : Act Science
If a drug is taken orally, then the concentration of that drug in the blood will rise to a peak concentration. Immediately afterwards, the elimination phase begins and the concentration of the drug in the body will fall exponentially. Each drug has a half-life (i.e. the time required for the drug's concentration in the blood to fall to half of its original value). Once the elimination phase has initiated, it typically takes four half-lives until the drug has been entirely eliminated from the body.
If an individual is given multiple doses of a drug over time, then the blood concentration of the drug will rise and fall periodically. This creates a graph of drug’s concentration versus time that will resemble a wave. The rising peaks of the graph occur immediately after administration of a dose, whereas the falling valleys occur as the drug is being eliminated. The inter-dose interval, represented by the letter
Experiment 1
A 125-milligram oral dose of a drug known as Cyclosporin A (CsA) was administered to an individual. The CsA blood concentration for this individual was then measured at various times over the next 24 hours. A graph of CsA concentration versus time was obtained.
Experiment 2
An individual was given multiple doses of CsA over a 60-hour period. The CsA blood concentration was monitored continuously. A graph of CsA concentration versus time was obtained.
Based on the results of Experiment 1 and the information in the passage, at which point does the elimination phase of CsA begin (assume the first data point is at zero hours)?
From hours 0 to 3 the concentration of CsA is rising. At 3 hours, it reaches a peak and begins to decline immediately afterwards; therefore, the elimination phase begins at 3 hours.
Example Question #41 : Chemistry
If a drug is taken orally, then the concentration of that drug in the blood will rise to a peak concentration. Immediately afterwards, the elimination phase begins and the concentration of the drug in the body will fall exponentially. Each drug has a half-life (i.e. the time required for the drug's concentration in the blood to fall to half of its original value). Once the elimination phase has initiated, it typically takes four half-lives until the drug has been entirely eliminated from the body.
If an individual is given multiple doses of a drug over time, then the blood concentration of the drug will rise and fall periodically. This creates a graph of drug’s concentration versus time that will resemble a wave. The rising peaks of the graph occur immediately after administration of a dose, whereas the falling valleys occur as the drug is being eliminated. The inter-dose interval, represented by the letter
Experiment 1
A 125-milligram oral dose of a drug known as Cyclosporin A (CsA) was administered to an individual. The CsA blood concentration for this individual was then measured at various times over the next 24 hours. A graph of CsA concentration versus time was obtained.
Experiment 2
An individual was given multiple doses of CsA over a 60-hour period. The CsA blood concentration was monitored continuously. A graph of CsA concentration versus time was obtained.
Suppose drug administration had continued past 60 hours during Experiment 2. Based on the results of Experiment 2, what would be the most likely concentration of CsA at 66 hours (assume the drug continued to be administered in the same exact way)?
In order to answer this question, we can continue the pattern displayed in the graph of Experiment 2. Notice that a trough occurs at sixty hours. If we look at other troughs in the graph, then it becomes apparent that about six hours after these troughs the drug reaches the following concentration
As a result, the concentration at sixty-six hours would most likely be as follows:
Example Question #50 : How To Find Data Representation In Chemistry
A chemist has found five substances in his lab without specific labels, named only A, B, C, D, and E. He hopes to find clues about the identity of each substance by dissolving each in hexane, a nonpolar solvent. He adds each substance to a different 
| Solute | Mass of Solute at Saturation (grams) |
| A | 11.1 |
| B | 23.6 |
| C | 0.23 |
| D | 3.1 |
| E | 0.11 |
Which substance has the highest solubility in hexane?
B
C
E
A
D
B
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